787 Batteries and Chargers - Part 1

[RR_NDB]

RetiredF4: (http://www.pprune.org/members/302846-retiredf4)

Hi Franzl,Sequence in (http://www.mlit.go.jp/jtsb/flash/JA804A_130116-130205.pdf)ANA (http://www.mlit.go.jp/jtsb/flash/JA804A_130116-130205.pdf), very probably: (http://www.mlit.go.jp/jtsb/flash/JA804A_130116-130205.pdf)

1) High temp at cells (to be understood why)
2) Cell #3, plus terminal (or # 4 minus terminal) shorted to battery case
3) Unlimited current (short circuit) flowed to aircraft ground return via battery case grounding wire. (~12 V at start of event)
4) Current of hundreds of Amps fused this battery case grounding wire.

[RR_NDB]

Hi,

Complementing previous post: (http://www.pprune.org/tech-log/505695-787-batteries-chargers-25.html#post7679260)

(Very probably)

Current (Hundreds of Amps) flowing due ~12V (cells 1, 2 and 3) was limited by ~1m Ohm (3 cells in series), contact of cell 3 (or 4) to battery case and battery ground wire.

This current stopped after plus terminal of cell 3 disconnected (destruction of it )

Very probably the plane landed with "NO DANGER". (Fuse was yet open)

Obviously without it´s main battery (no availability of energy due open circuit)

PS

Ground wire probably was cut in the right. In the left, shows damage due high current.

[RetiredF4]

Here is a rough google-translation of most of the nicely painted text

Serious incident investigation aviation
• All Nippon Airways Co., Ltd. plant genus (Flight 692)
• The expression of type type Boeing 787-8 formula
• JA804A registration symbol
• January 16, 2013 date and time of occurrence at around 08:26 (Wed)
• FL 320 near Airport Takamatsu
February 5, 2013

1. Overview of the main battery
• the machine is equipped with two battery
● Main Battery
● APU Battery (APU: Auxiliary Power Unit)
• battery lithium ion both the same
• eight cells connected in series
• The performance is as follows:
Lithium-ion battery
· Nominal voltage: DC 29.6V (3.7V × 8 cell)
Nominal capacity and nominal capacity of: (at An'a) 75Ah
• Weight: 28.5kg
· Size: 215H × 280W × 335L (mm)
(According to the manufacturer's documentation)

2. Location of the battery

3. Survey Battery
■ APU battery and the main battery
· Japan Aerospace Exploration Agency (JAXA, Mitaka), carried out the
CT scan
· The main battery manufacturer in Kyoto performed scan
CT for each cell, the decomposition study
■ Battery Battery Monitoring Unit (BMU)
-Manufacturer in (Fujisawa), conducted a survey
■ Battery Charger
-Manufacturer in USA, conducted a survey
■ contactor and battery diode module (BDM)
-Manufacturer in France, will study

4. CT scan image
CT scans into 3D images taken with the APU battery JAXA

5. Degradation of the battery in the manufacturer's

6. Appearance of the cell (main battery)

7. Appearance of each cell (main battery)

8. CT scan image of each cell

9. The status of the battery cell (Summary)
■ damage seen in all eight cells.
cell 3 and cell 6 damage is particularly large
■ thermal damage can be seen in all cells
■ can be seen before thermal runaway
■ The positive electrode of the cell 3 large damage
and large damage cells 8 and 1
Damage is great for other cells 7, 8, 2
■ Except for cell 4 and cell 5
Cell 6 Six positive electrode of the cell
Observed in the internal fusing

10. Other
Ground wire of the battery casing is cut

Summary
■ Need study in more detail the circumstances of the cord, a battery-cell damage further investigate the situation further damage battery
Research and degradation
■ Need to continue to find the cause of the damage
analysis and data recording device, such as flight, Battery charger etc.
■ Need to continue the investigation of the disconnection of the grounding wire enclosure, timing and causes.


If somebody can do it better or an english version is available feel free to ammend.

[hetfield]

Nominal capacity and nominal capacity of: (at An'a) 755Ah

755 must be a typo...

[Lyman]

I think a summary. A brief one.

Have not seen anything here that was not addressed by all concerned in the development and certification process.

Best efforts, best practice resulted in uacceptable failure trail, BY DEFINITION. The regulations were too minimal. If "Relaxed" to accomodate continued use, the Regulatory paradigm becomes a laughingstock, instead of just a wink wink....

At the very outset, the sham 'specials' were an obvious permission slip to utilize a technology that cannot be made safe for aircraft in commercial carriage. The recent hasty "Permission" to transport this "cannot be made safe" technology on aircraft only emphasizes the desperation of a failing attempt to salvage it.

I think Lithium Ion power on aircraft is done.

[green granite]

Nominal capacity and nominal capacity of: (at An'a) 755Ah 755 must be a typo...

I think it is a typo for 75.5Ah which is the nominal capacity for the battery right down to fully discharged and is rendered U/S. The 65Ah is the capacity available for normal usage ie before it enters the 'knee' part of the discharge curve.

[RetiredF4]

Quote:
Nominal capacity and nominal capacity of: (at An'a) 755Ah
755 must be a typo...

It is. I corrected it.

[USMCProbe]

This thread has gone thermal runaway.

LI batteries are as proven, and maybe more, than any other battery technology, ever. Does your Iphone or laptop have a placard that says "charge only 5 meters from a flammable object, and never indoors?" How about your Makita LI powered drill?

How many of us have had a Iphone or laptop battery ignite?

Every aircraft that takes off and lands has a couple of hundred LI batteries in the passengers luggage. These batteries are not aircraft rated. They are the cheapest pieces of crap that any company could source, charged by the cheapest piece of crap charger that can be sourced. In Asia you can by a charger for less than 2 dollars, and a 2100 mah battery for 7 dollars. I have 4 in my bag right now. I have carried them on hundreds of flights, and the aircraft did not self-immolate.

A 787 sized aircraft carries 20,000 gallons of combustible jet fuel. Bigger aircraft much more. All jets other than a 787 have pneumatic pipes that carry engine bleed air at 100-700 degrees C, all over the aircraft. In effect, these pipes are carrying fire all over the aircraft.

What we are talking about is two little cubes of electrical charge. A couple cubic feet each, and 70 lbs. The only time it went completely nuclear, the thermal damage was contained.

If I were to put my own money on the line, I would bet Yuasu makes the finest lithium batteries on the face of the earth. Thales designed a box that contained the thermal damage. Somewhere there is a single fault that caused these problems. It will be found, and fixed.

My guess? Possibly 2 defective chargers from Securaplane. Or a specific set of aircraft equipment, operated very occasionally together, that put noise/AC/spikes into the aircraft grounding system, and that affected the charging.

Going away from LI? OK, lets just go back to land line phones, desktop computers, etc. Typewriters and sliderules?

LI is proven. It is safe. It is not perfect, and it has its limitations.

If you want to eliminate fire hazard on an aircraft, maybe it is better we stop carrying jet fuel? 747's probably carry 50,000 gallons of it. And a few feet away is high temperature engine bleed air, coursing through pipes, in a wing swinging up and down several feet, during turbulence.

This battery problem, in the end, will be a zit on a bug's arse. It is nothing compared to the engineering that has made commercial aviation, consumer electronics, automobiles, etc, SAFE.

A hundred post ago this thread was great. It is now turning into......PPRUNE.

[Lyman]

Yes, probably too many......opinions? :)

[USMCProbe]

The first 400 opinions were pretty good. Everybody added in a little knowledge, and asked a few questions. I learned a lot. It was the best thread on PPRune I ever read.

But I fly airliners, and in the grand scheme of things, this is minor, and no one got hurt. The system worked.

If you compare the BTU heat storage of these batteries, with the BTU storage of the fuel in the wings, and the airborne fire coursing through the bleed air systems of all other aircraft, this is really minor.

And the system worked. All of it. No one was hurt. They will come up with an interrim fix and probably an MEL procedure for the mechanics and flight crew. In a year, they will have the problem solved, and aircraft retrofitted with a permanent fix. The MEL will then be rescinded.

There are some really bright contributers to this thread. Anybody, like me, that read it, all learned something. In my case, I learned a lot.

I am concerned that Boeing overstepped in their outsourcing. But I am sure they figured that out as well. More than likely, they outsourced so much, they didn't have the in-house ability to troubleshoot the problem. They learned that as well.

[TURIN]

Indeed.
Lyman. That is not explosive damage, it is a tear. Fire fighters are tough and carry axes.

[FlightPathOBN]

The issue isnt simply the batteries, it is about the process. The process of self-certification is an issue, but the assembly of the aircraft, much like the battery system, was manufactured by a myriad of suppliers, with final assembly at the Boeing facility.
The battery system involves at least 4 different manufacturers, multiply that throughout the rest of the systems on the aircraft.

Somehow, the battery system got through the process, so now, there will be emphasis on the rest of the aircraft.

Look how much of the aircraft was fast tracked, I bet the FAA is right now.

(actually, USMC, I dont feel that the containment system worked. That thermal runaway that happened at the APU was not contained, and if that had happened at the front, the avionics are right there....)

[RR_NDB]

Hi,

Probable major short circuit path

http://i50.tinypic.com/260pv0k.png

PS

Other paths, after cells reaching high temperature may have occurred

The opening ("fused") of connection of plus terminal of cell # 3 to minus terminal of cell # 4 probably spared high current (hundreds of Amps) flowing through # 4 and # 5.

Cells # 4 and # 5 were spared because voltage of plus terminal of cell # 3 went to battery case.

http://www.japantoday.com/images/size/x420/2013/02/urn%3Apublicid%3Aap.org%3A6b5d91aed883404f958085df1617369c.j pg


Other paths, after cells reaching high temperature may have occurred.The bad condition of cell # 6 may be explained by a secondary path to battery case.

The major path, in my model "hit severely" cells # 1, # 2 and # 3.

JTSB: Source for this model (http://www.mlit.go.jp/jtsb/flash/JA804A_130116-130205.pdf)

[Lyman]

Hi USMC

I appraciate your posts, and I too am learning a great deal. I'll try to stick to evidence, and if an opinion, a quote from a professional.

to wit

“I always consider the separator as a major source for a problem” Dr. Abraham says of the sheets that are 25 microns thick, around the same thickness as cellophane.

He references the polypropylene separator material that comprises a discrete "electrode".

and

Each of the three windings is approximately ten meters long providing more than 35,000 square centimeters of separator surface area where a single hole could lead to a short circuit between electrodes.

here a reference to the continuous nature of a single layer. So here I refer to my question as to suitability of subjecting such fragile material to a zig zag pack where each "return" in the continuous "wrap" puts stress on a "fold" in the "cellophane".

For reasons (by reference) to Musk, a cylindrical method of winding would eliminate "corners" in a flat "fold pack". Too, it would create a cylindrical shape, locating the remotest part of the wind (the Axis, or "center") closer to the external border, and cooling external space.

and

“Once the polypropylene is breached you have an internal short” says Dr. Abraham. “Once they internally short, there is little you can do to stop it, it goes off like a rocket.”

So allow me to wax optimistic. If these actually are "flaws", and I think they likely are, then the separator material can be thickened, perhaps a better medium selected, a different geometry for the winding, and a somewhat larger, cooled case can be built for the "eight battery group". (my term).

The discouraging thing is that BOEING knew all this in 2006. And here we are.

I know Musk is in bloody competition with BOEING v/v lowE/orbit, but in my experience, when one wants to produce the very best product, one does not ask one's friends if the design is "best", one asks one's enemies, at least by proxy.

thanks for the redirect USMC.

[Machaca]

Lyman a technology that cannot be made safe for aircraft


To assert this you must already know exactly the mechanisms of the failures. :ugh:

Regulations cannot and will not prevent an occasional sub-par component from being installed onto an aircraft; whether it be a tire, fan disc, or battery diode.

[Lyman]

Hi Machaca

I know you resent my presence here, and I am sorry it upsets you.

I do not "know". I do believe BOEING knows. I also believe BOEING knew prior to the dramatic fires and problems that caused the grounding.

I think the BATTERY is the problem. I think the construction and design create problems that can barely be mitigated, and cannot be eliminated without changing this design.....

So if the chemistry of this application is to survive, and Lithium technology made safe, changes will be made.

I wish I had stated that before you assumed I "knew" what the problem is.....If I had, I think it is fair to say we are not terribly far apart in our positions.

Because my issue is what BOEING knew, and when did they know it....and the implications that had for certification, continued flight, and 'Regulation".
It is patently obvious the technology got special consideration, that it failed to live up to the expectations written into the regs, and that at the very least, both Boeing and FAA knew it would be close......real close as to whether the LiCoO would cut the mustard.

I will not believe it when they say, and they will...."We had no idea....It is simply a mystery as to why these failures caused problems...."

Or, "Why these problems caused failures....." a twofer. Covers it both ways.....

:ok:

[Rocchi]

Looking at RR_NDB's link to the Japanese report and the image on page 7, the terminal post on top of battery no. 3 is gone and burned away as is part of the connecting strap. My question is, 1. Could mechanical damage to the battery have been caused at assembly by over torquing the connector strap nut? 2. As the nuts on the battery posts do not appear to have any locking or self locking properties, could it have come loose and thereby caused arcing.

[Old Engineer]

No time to comment, but to repeat a famous quote, "I shall retun."

Your orders for the day are to redesign the battery space to hold a NiCad or NiMH if that becomes necessary. Find a separate space for the battery. Locate it under the potable water supply.

If I'm still away, look into air-locking this space, outer door opening down...

Remember that if 3 weeks have not sufficed to find this problem, it may never be found.

[RetiredF4]

@UMSCProbe

You are entiteled to your post and and like ever there is some salt in it.
However, the safety of the 787 Dreamliner with the present battery arrangement is seen unsafe for future flight in it´s present state by the regulatory authorities, not by PPRuNe posters on this thread. And i think they made that decision with judgement and wisdom.

It´s meanwhile obvious that the Li-Cells alone can´t be the problem, the integration into the airframe and its asociated systems and subsystems might be. Contributing might be implantation of the 8 cells into the battery case. This one looks like some 15$ metal case i could built out of pieces available in my garage. It did not contain the event as it should have, and how the nut of cell 3 could survive the burndown of the bolt it was fixed to without any melting damage will be an interesting question.

[grebllaw123d]

On the spec. for the cell in the B787 battery, http://www.s399157097.onlinehome.us/SpecSheets/LVP10-65.pdf ,it is stated that the "Maximum discharge rate" is 5.0 A.

Does it mean that you can take out a max. of 5.0 A from each cell at any given time in order to supply the associated consumers?

[RR_NDB]

Hi,

Rocchi:

Good question! (http://www.pprune.org/tech-log/505695-787-batteries-chargers-26.html#post7679919) Low or high torque are not good. Low IMO is worse. Could overheat the connection.

The model i imagine is another: Heat, short to case and LOC. :)

Your point could be one factor to damage (cell # 3).

Welcome!

[Lyman]

I think at least in ANA, the stainless case contained the event. The "top" is deformed, having been subjected to sufficient pressure to significantly bulge the structure with the fasteners preventing separation....

[FullWings]

If you compare the BTU heat storage of these batteries, with the BTU storage of the fuel in the wings, and the airborne fire coursing through the bleed air systems of all other aircraft, this is really minor.
I'm not sure this is a totally valid comparison. The fuel is inert on its own and the bleed system can be shut off as soon as abnormal temperatures are sensed. If the wings carried a mixture of LOX and kerosene, then yes...

And the system worked. All of it.
Errrrm, not really? Uncontrolled fire in one aircraft on the ground, meltdown and discharge of battery internals in another, leading to an emergency landing and evacuation? What would a non-working system look like? :confused:

There is more energy in half a pound of butter than in an average grenade but which would you rather hold in your hand? Now pull the pin.

It just appears to me that the combination of cobalt chemistry and a lot of high-capacity cells jammed together isn't the right way to go for anything that flies. Or drives. Or floats...

[saptzae]

@grebllaw123d

Rating is 5 * C (A). C is 65Ah. 5 * 65 = 325A

The inverter powered starter motor soft-starts and draws well below the the battery limit.

@hetfield
Yes, lead acid can do it, Li-Ion not.
No, lead acid can't either and also consists of sub-cells.

[Lyman]

Failure mechanism, example.....

Quote......
"The use of copper as the current collector for the negative electrode has particular reliability and safety implications. At very low cell voltages (usually approximately 1 V for the cell), the potential at the copper current collector increases to the point where copper will begin to oxidize and dissolve as copper ions into the electrolyte. On subsequent recharge, the dissolved copper ions plate as copper metal onto negative electrode surfaces, reducing their permeability and making the cell susceptible to lithium plating and capacity loss. Usually, once a severe over- discharge event has occurred, cell degradation accelerates: once the negative electrode has become damaged by copper plating it will no longer be able to uptake lithium under “normal” charge rates. In such an instance, “normal” charge cycles cause lithium plating, which result in a greater loss of permeability of the surfaces. Ultimately, over-discharge of cells can lead to cell thermal runaway." ....Unquote

http://www.nfpa.org/assets/files/pdf/research/rflithiumionbatterieshazard.pdf


So it would seem that "internal protections" would be limited practically to a strict control of voltage within a frame of charge/discharge. protection from mechanical damage, and environental stressors are straightforward, nothing below -18 or above 60 (C).

Since the listed resrictions are "mitigating" rather than "prohibitive" (eliminating) as to failure, they can certainly be construed as "permissive of" smoke, runaway and even fire "events". A "mitigation" is by definition "may" not "may not"....

[bill good]

On the question of containing a problem within a cell. How many prismatic shaped pressurised aircraft are flying? The question on the backup internal protection is where the fault will be found. I cannot find the same sort of protection built into the prismatic cells as can be found within the cylinder type which has at least 2 methods to prevent this sort of trouble. What I would like to find out is if there was power being feed back to the batteries in both cases while this fault condition existed or if the process of disassembly was all within the battery case. i.e the one on the ground- was ground power or APU supplying DC to the batteries & I assume the A/C flying had the main battery powered from its charging source. By design, if the battery is fully charged it should be disconnected to protect the aircraft (imo). Li-Ion has no loss of capacity over any flight time of any aircraft. All the Aux. battery does is to start the APU when Ext, AC power is not available after which the AC alternators provide the systems power for normal ops. (maybe needed to "clean up" the DC but that could be addressed) There are several issues not just one cell failure that must be addressed before this aircraft is returned to service on just how safe the interface is to other components within the DC system. I hope all are identified.

Hopefully the fix is close.

[TURIN]

Bill, the battery does not start the engines.
The APU battery can be used to start the APU if no other AC available.
Main engine start is from high energy AC sources only.

[RR_NDB]

Hi,

FullWings @ # 523

"It just appears to me that the
combination of cobalt chemistry and a lot of high-capacity cells jammed together isn't the right way to go for anything that flies. Or drives. Or floats..."

And for anything in ground too. So the question is: Why the cell(s) started to overheat?

The "equivalent circuit" derived from a visual analysis of the ANA battery shows clearly the temperature inside the case was so high that caused a dramatic short circuit that "fused" an intercell strap and a thick ground wire. I tend to think as the increasingly hot cells inside the case like you put created the short circuit of cell # 3 to ground. (~ 12 V applied in resistance of miliOhms. Surge current of hundred Amps. (probably thousands Amps).

I don´t put as probable a short circuit as the trigger of the battery destruction. FDR iirc data is compatible with the model i presented.

[saptzae]

@RR_NDB

The ground strap shows little thermal damage and its cross section is too small to have carried any significant current in destroying #3.

The ground strap was likely mechanical damaged and partially cut either before the event or by intervention.

Severe damage seen is tertiary. I would not spend time on it.

Important is Primary failure, cause of deterioration leading to shorting cell and Secondary failure, if/why the battery was not protected from charging.

Edit: If ground strap was cut pre-event and could have touched BMU PCB, it possibly could have induced the battery failure.

Edit: Arcing at the pole of #3 due to loose nut, I think it would have welded shut, not burned the pole off.

[bill good]

Ths Turin, I was focused on the local problem at the battery installation level!!
I hope it reads correct now.

Anyone able to give min voltage alowable before dispatch for this A/C?

[RR_NDB]

Hi,

TURIN,

JAL APU at BOS was started by AC or from battery?

A model i am imagining is:

1) Batteries discharged (for many possible reasons) more than expected
2) Thermal aspects (cell heating, improper thermal cell monitoring, inadequate battery case, inadequate cell spacing) created conditions for thermal runaway (a positive feedback that in the end destroy the device)

So, my question is because ANA 787 main battery very probably was being recharged (hi curr.)when event started.

BOS JAL APU battery probably was also being recharged? (high curr.)

My feeling, was NOT.

[FlightPathOBN]

I'd like to see some of the other 99 batteries they replaced, and some images of what the battery box looked like when the fault messages showed up...

[RR_NDB]

Hi,

Saptzae @ # 529

First i need to clarify some points to prepare my comment.

1) Destruction of # 3 was by what? Internally generated heat (due subcell inbalance, dendrites, voltage), ohmic losses due thousand Amps flowing to case (and ultimately to ground), or what?

2) On ground THICK wire you has two details: One seeming mechanical and another VERY PROBABLY caused by excessive current. Please refer to the equivalent circuit where i put the (highly probable due evidences) short circuit path.

3) Severe damage shows a PATTERN. It´s up to us to establish a model rhat if is robust enough could explain most. I am just taken into account everything. Could we discard sabotage? Answer is NO. I prefer look to all details and balance them in the best proportions.

4) Shorting cell? Which one? Due over voltage, improper charging? Temperature of individual cell(s) not being measured?

5) to be continued...

[FlightPathOBN]

RR,

I would suspect the way the cells are wired as well...not with bus bars, or ground straps, but simple braided wire...

and I certainly would not consider this 'thick' wiring by any definition...

[saptzae]

@RR_NDB

First i need to clarify some points to prepare my comment.

1) Destruction of # 3 was by what? Internally generated heat (due subcell inbalance, dendrites, voltage), ohmic losses due thousand Amps flowing to case (and ultimately to ground), or what?
I continue to rule out thermal runaway as cause of Primary failure. My scenario is same as at BOS, the same pattern. Primary failure was in #3 (#5 at BOS) due to deterioration of unknown origin. Secondary failure overcharge and thermal runaway of several other cells. Tertiary failure is total destruction of #3, how the pole can burn away, leaving the nut unscathed, beats me. The cause of "deterioration" leading to Primary failure remains as elusive as ever. By now, NTSB could have said something, perhaps them looking for micro-shorts by testing last week gives a hint toward the short of a cell as the cause of Primary failure.


2) On ground THICK wire you has two details: One seeming mechanical and another VERY PROBABLY caused by excessive current. Please refer to the equivalent circuit where i put the (highly probable due evidences) short circuit path.
Yes, it could be that the frayed, not severed wire burned up the way you suggest. It could also be that the severed wire caused shorts on a BMU PCB. Now, that would be really awkward and destroy the pattern of both batteries and feed sabotage conspiracies.


3) Severe damage shows a PATTERN. It´s up to us to establish a model rhat if is robust enough could explain most. I am just taken into account everything. Could we discard sabotage? Answer is NO. I prefer look to all details and balance them in the best proportions.
I think it is tertiary damage pattern, like structural breakup, it can go any way.


4) Shorting cell? Which one? Due over voltage, improper charging? Temperature of individual cell(s) not being measured?
#3, (#5 at BOS), deterioration of cells by mishandling after assembly** / by maintenance or mismanagement by BMS during flight operations.

** I don't know how battery could be safely assembled when cells carry a charge. Any mistake like a short would lead to a firework or damage. Perhaps, battery is assembled while cells not carry a charge, and are charged after assembly.

I am not confident about cause of deterioration leading to Primary failure.

Mishandling like for example resetting BMU cutout of deep discharged battery, thereby charging damaged cells would be a convenient and fixable explanation. Mismanagement by BMU would be harder to fix.

If I would want to figure evtl mismanagement out, I would connect transient processing by way of a 8 channel differential 12bit transient recorder at 1megasamples/sec to the battery, one channel per cell and perform real-time transient analysis to find unique voltage transients on cells.

I feel confident toward the Secondary failure pattern, it is a very tough job for BMS to detect cell short in a timely manner. That will have to be fixed. It may well take something like the above mentioned transient processing to be responsive enough. Another way could be an infrared camera in the case. BTW, Temperature sensors would be not much use as the response is way too slow.

Tertiary failures - breakup - I don't really think about.

It all may well boil down to lack of understanding in a highly decentralized operation. Examples are that nothing seems to have been done about deep-discharged and failed batteries over many months.

Edit: BMU -> PCBs in battery box. BMS -> BMU + charger + all other related functionality.

@FlightPathOBN
I would suspect the way the cells are wired as well...not with bus bars, or ground straps, but simple braided wire...

and I certainly would not consider this 'thick' wiring by any definition...
The cells are connected using at least 350A rated bus bar and the wires are only for monitoring and balancing at currents below 5A.

Edit: I also would like to see CT scans of in-service as well as of failed batteries.

[FullWings]

RR,
And for anything in ground too. So the question is: Why the cell(s) started to overheat?

Agreed. Reading through this thread there are many cogent theories as to why the overheat began and I have to say most of them seem at least possible.

The main question for me is: why did batteries whose technology was known to be vulnerable to catastrophic thermal runaway (more than virtually any other kind of cell) get put into a configuration that sent the whole lot up in flames if there was a *single* failure? Who in their right minds would install that in an aircraft that could be 3hrs from the nearest airfield?

If it had been designed to contain an individual cell going AWOL, then you'd get something like a status message "ELEC BAT MAIN SYS" which would show reduced redundancy in flight and maybe no dispatch at the other end until the problem had been sorted. You don't expect (or want) a large percentage of the chemical energy in the whole battery being released over a short period of time inside the aircraft... :ugh:

Looking at it from a statistical POV, if all it takes is a microscopic rupture in a nanometre-scale film in one cell to trigger a destructive event, when there are 800 787s flying 18hrs a day carrying (insert number) of cells, how likely does this become?

[cockney steve]

Regarding the number of batterie that have been changed-out.-

First, one has to go along with the officoal viewpoint at Certification....."safe, well-proven, long service-life......."

So, What we're looking at, is an overgrown cellphone or Laptop battery.

they cost a fraction of (16,0000 USD?) the price of the Thales "box of energy" They're charged by non-technical and sometimes low-intelligence owners ,using cheap and nasty power-supplies.

IT ALL WORKS MILLIONS OF TIMES BETTER THAN THE "SCREAMLINER" SETUP

The number of documented failures have been a minute percentage of the Thales failures.

All these "Domestic" batteries are properly fed/controlled by their interface circuitry.

When your phone needs charging, it switches itself off....you connect a supply and it automatically "sees" it and commences recharging....does this for hundreds of cycles.

So, WHY is the "screamliner's" system so pi55-poor that it won't stop an over-discharge but instead converts it to a disposable?

The lack of sub-cell monitoring and the whole lack of fitness for purpose makes one think of short term profiteering.

For whatever reason, Boeing plumped for the most sensitive and unstable of the Lithium technologies.

You would have thought that the person(s) making that decision, would have used every resource available to ensure that it worked properly.

they didn't ......it doesn't. someone has a lot to answer for. that many "dead" batteries in that short an operating-life points to a major problem......so, who was brushing it under the carpet?


If the volume of components ordered is twice the number that the customer can use (new-builds) the balance is going somewhere.....in this instance, a massive pile of replacements well before their anticipated service-life.

I feel there's a lot we don't know, as yet.

[TURIN]

When your phone needs charging, it switches itself off....you connect a supply and it automatically "sees" it and commences recharging....does this for hundreds of cycles.

So, WHY is the "screamliner's" system so pi55-poor that it won't stop an over-discharge but instead converts it to a disposable?



I think this was covered in either this or one of the other (five?) threads.

In an emergency you don't want your battery to shut down just to save itself from the scrap heap.

Imagine this scenario.

Full inflight electrical supply failure (doesn't matter why-lets call it fuel starvation so no APU either. The Airtransat A330 gliding into the Azores springs to mind.)


The main bat kicks in while the RAT drops and spins up.

The a/c lands safely due to excellent pilot skills:E but on the roll out as the RAT winds down due to lack of airspeed, the brakes are being powered by the main battery. The battery monitoring system at this point senses a low charge state and shuts the battery down. Pilots get a black screen, microsoft windows icon, the words "hibernating" flash on the PFD and a little yellow box pops up and says "please connect external power or change to a new battery".


Meanwhile, the poor chaps at the front end are smashing their feet through the brake pedals as the end of the runway looms at about 140kts.

OK I'm being facetious, and you could argue that a simple logic based on air/ground, airspeed, wheel speed etc should be incorporated to stop that.

Maybe it was suggested and dismissed as unnecessary expense/weight/design complication. Who knows?

[TURIN]

Hi,

TURIN,

JAL APU at BOS was started by AC or from battery?



No info on that sorry.

In normal ops the APU would have been started on taxi-in off the normal AC supply. However, in my experience it is not uncommon for the ground electrical supply to drop off line (after engine and APU have been shutdown) requiring the APU to be started off the battery.

Happens a lot where I work as the airport infrastructure is diabolical in regard to suitable multiple 90KvA supplies.

[Lyman]

Separator
Lithium-ion cell separators most commonly are porous polyethylene, polypropylene, or composite polyethylene / polypropylene films.29 These films are typically on the order of 20 μm thick, although thinner (approximately 10 um) and thicker films can be found (approximately
40 um). The function of the separator is to prevent direct contact between the anode and cathode. The pores in the separator allow transfer of lithium ions by diffusion during charge and discharge. These films soften and close their pores at elevated temperatures (usually in the range of 130 to 150°C / 270 to 300°F), and stop charge or discharge processes by impeding the transport of ions between the anode and cathode. Thus, these types of separators are commonly referred to as “shutdown” separators. If a minor internal short occurs within a cell (e.g., from small contaminants penetrating the separator), local separator shutdown will effectively disable a small point within the cell by melting slightly and closing the separator pores (Figure 13). The shutdown function will also permanently disable the entire cell in the case of an abnormal internal temperature rise to approximately 130°C (266°F) (e.g., due to high current draws caused by an external short circuit of the cell) (Figure 14). However, should internal temperatures rise

This is where the problem is... If Boeing admits it is this simple, they will not lose some face, their face will fall completely off....

[Lyman]

An organic corollary.....

Imagine the human brain suffering random amyloid deposition (sclera) that block neural pathways, and cause the brain to lose efficiency...

Yuasa's batteries have rapid onset Alzheimers....

Leave them alone, save them for emergency supply needs only.

Unless the charge range and heat cycle can be rigidly, completely controlled...

Fragile, these little boxes....

[syseng68k]

Interesting update mentioned in r&n:

Boeing Plans Battery Redesign to Get Dreamliners Airbone Again | Frequent Business Traveler (http://www.frequentbusinesstraveler.com/2013/02/boeing-plans-battery-redesign-to-get-dreamliners-airbone-again/)

A couple of weeks or so ago, I was trying to determine if each cell
had it's own associated temperature sensor, rather than one to cover
the whole enclosure. The following from the above article suggests that
there may *not* be one per cell:

"Boeing may <snipped> possibly add better heat sensors".


I seem to be the only one out of step here, as everyone else
still seems to be obsessed with the battery and it's construction,
but there are other possibilities to consider.

Still think that the battery would only fail in such a way if it
were abused, which suggests either operation outside cell voltage
limits, or inadequate cell temperature sensing, during fast charge
or high current load.

Might need just a software mod to fix, though after all the hysteria
only an ejectable, fully armoured enclosure would
be good enough for some :*...

[USMCProbe]

I just went out and had a 6 mm thick SS enclosure fabricated for my Galaxy S2 so I don't self immolate with it in my pocket. I also put a 100mm spacer between the battery and the phone so it doesn't short out. I have 3 temperature and pressure sensors installed, hooked up with Bluetooth to my headset, to warn me about impending doom. All of this so I can hook up my cheap 2 dollar knock off charger to my 7 dollar knock off Chinese battery. I believe everybody should have this setup and am going to demand all government safety bodies implement these measures immediately.

Does this sound silly? Of course it does.

This is extremely mature technology, that has a minor flaw that will be fixed.

All the short circuits were effects, not causal. You can put all the space between cells you desire. You can put 100 meters between each cell, but the cells will still short circuit internally if they heat and swell up. This is thermal runaway.

Extra sensors, in an aircraft? Maybe. I would vote yes.

[FlightPathOBN]

From Boeing Land...
The National Transportation Safety Board (NTSB) has pinpointed the start of the 787 Dreamliner battery fire on a parked Japan Airlines jet a month ago today as a short circuit inside a single cell.

The agency still hasn’t identified the cause of the initial short circuit but has narrowed down the suspects.

Details provided by the NTSB make clear that Boeing will have to redesign the battery for a long-term fix.

In addition, the NTSB pointed to failures in the airplane certification process conducted by Boeing and the Federal Aviation Administration (FAA), which failed to identify the hazards revealed by this incident.

“The assumptions used to certify the battery must be reconsidered,” said NTSB chief Deborah Hersman in a detailed press briefing. “Our task now is to see if appropriate layers of defense and checks were built into the design, certification and manufacturing process.”

NTSB questions Boeing&rsquo;s 787 battery design and certification after short circuit | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2020307773_ntsb787xml.html)

[syseng68k]

USMCProbe:

I just went out and had a 6 mm thick SS enclosure fabricated for my
Galaxy S2 so I don't self immolate with it in my pocket. I also put
a 100mm spacer between the battery and the phone so it doesn't short
out. I have 3 temperature and pressure sensors installed, hooked up
with Bluetooth to my headset, to warn me about impending doom.

All of this so I can hook up my cheap 2 dollar knock off charger to
my 7 dollar knock off Chinese battery. I believe everybody should have
this setup and am going to demand all government safety bodies implement
these measures immediately.
So long as you realise that the phone would no longer function as a
phone, due to the sceening ?, but hey, it's still got the rest of it's
functionality, games, camera at both sides etc etc. Seriously though,
such irony may be lost on many, who would have this drag on for as
long as possible.


This is extremely mature technology, that has a minor flaw that will
be fixed.
Of course it is, but there are deficiencies in this particular design,
otherwise the batteries would not have ended up in the state that they did.



Extra sensors, in an aircraft? Maybe. I would vote yes.
Most likely, though I suspect that improved battery management will
be the key to solving the problem. Can I say that again ?. At least
it appears as though they are (finally) looking seriously at that
area (charger, BMS) now...

[Lyman]

USMC

All the short circuits were effects, not causal. You can put all the space between cells you desire. You can put 100 meters between each cell, but the cells will still short circuit internally if they heat and swell up. This is thermal runaway.

Technically, I agree. Cause? Shutdown syndrome. Each Separator fault at the "Capillary" level occludes a penetration, preventing Lithium ions from transiting the separator. This creates heat, and a degradation of battery CAPACITY, which "ages" the cell. The range of permitted charge level narrows, the battery degrades. Eventually the cell produces a thermal runaway, and we see JAL, ANA.

The best way to remedy the problem is to wind the cell radially, not "folded".

The prismatic shape and the folds produced, cannot dissipate heat quickly enough, or efficiently enough, to ennable a long life and efficient profile for the "Eight battery group" as built by YUASA.

It's the BATTERY....

And BOEING'S immature pride, and stubbornness in trying to push a bad position.

:ok:

[syseng68k]

Lyman:


The prismatic shape and the folds produced, cannot dissipate heat quickly
enough, or efficiently enough, to enable a long life and efficient profile
for the "Eight battery group" as built by YUASA.
So, what about all the other applications for these cells, for which we
have no news of any problems ?. As I said in an earlier post, they
have been approved for use by NASA, the ESA and others only after very
extensive testing, so are they all wrong ?.

The whole idea is for the cells not to overheat in the first place, for whatever
reason and that's down to good design for the bms..

Battery topology really doesn't matter, so long as they are operated
within data sheet limits. All li chargers utilise temperature sensing and
should backoff charge current to avoid overtemperature. Sensing is
critical, hence the earlier disussion about individual cell temperature
sensing, as opposed to overall enclosure sensing.

Laptop batteries may get away with a single sensor, but it's just not
enough for an enclosure of that area. If there's adequate sensing, the
cells won't overheat to start with.

Of course, this doesn't cover the high rate of discharge case, such as
apu starting, but once again, the battery can be safely disconnected from the
load if excessive temperatures are seen by the bms...

[Lyman]

Chris.

with great respect, you are absolutely right. So too, am I. In your recent post your questions all have answers. My interpretations of the problems and the solution are based on prior art, prior knowledge, and I create an interpretation.

Architecture, partially, Control/management, parenthetically. Application, absolutely.

In post #525 I quoted what I perceive to be the basic and fundamental problem.

For YUASA. BOEING did not feverishly replace the BATTERIES because they thought the chargers and controls needed replacement.

OCCAM.

One more time. BOEING knew. All along. There is no mystery.

The current charade is a produced drama.

Too bad BOEING is too sick to admit the problem, fix it, and start flying.

PRIDE can be way expensive.

[Lyman]

Chris. I think the separator will be upgraded, thickened, and a better method of perforating the film will be found. Also, I believe quality of paste, and applicating method will be upgraded. Of course I think cylindrical shape will be utilized, if it can be demonstrated that it will peform in a Battery of this capacity and size.

I wanted to say ceramcs will play a part, but I think that is a way off, plus the possibility that in an explosion, ceramics will fracture and become shrapnel.

Hersman claims the method of certifying the technology will be examined.

YA THINK?

[syseng68k]

Lyman:


Chris. I think the separator will be upgraded, thickened, and a better
method of perforating the film will be found. Also, I believe quality of
paste, and applicating method will be upgraded. Of course I think cylindrical
shape will be utilized, if it can be demonstrated that it will peform in a
Battery of this capacity and size.
Sorry, but that's just guesswork without any of the required science. Perhaps
ok in r&n, but tech log ?. Just because one man who has experience of the
technology for a different application says it's wrong doesn't mean that
this design is wrong. If the cells are managed properly, then there should
never be a problem. If the cell management fails, then anything might happen,
so perhaps the enclosure and cell mounting should be revised to better
account for worst case conditions. I'm not qualified to comment on that
though.


I wanted to say ceramcs will play a part, but I think that is a way off,
plus the possibility that in an explosion, ceramics will fracture and
become shrapnel.
Kevlar or carbon fibre ?. Perhaps they use that for intercell spacing
already ?. Internally, such cells can use an interplate material that's designed to
be self healing.


Hersman claims the method of certifying the technology will be examined.
New technology and new application of a sensitive technology may need a
different set of design rules to standardise usage for aviation.

For those who are not engineering bods, will try and get an image together
that describes the overall charger - bms - battery system. While the battery
enclosure layout might have been better, you can't consider such a failure
by looking at any single item in the system. You have to look at the whole
system and understand how each part interacts with another.

While we only have limited information, it should be possible to work out
how all the bits fit together, their interactions and possible failure
modes...

[Lyman]

Any method of winding will disguise almost all the surface area of the separator.
Since each failure begins at a perforation in material that is twenty five microns thick, the capability to monitor all the area is impossible, and sampling the entire cell is not sufficient.

I am sorry, it is not guesswork. It is based on knowledge I have researched, and based my intrpretive skills upon.

Kevlar and Carbon fiber (sic), are not stable in these temperatures, and off gas.

Ceramics is a natural, even as a suitable separator, in and of itself. Porous, heat resistant, and non conductive.

As to certification, the FAA relied almost entirely on the applicant, BOEING, to write its own rules.

I am grateful for the opportunity to have this discussion, Chris.

[Machaca]

For a better understanding (and hopefully avoid endless conjecture) of the prior art vs the new art of packet cell construction, here's a glimpse into patent 7629077 awarded to some smart lads at Qinetiq Ltd:



Prior

http://i337.photobucket.com/albums/n385/motidog/battpriorart1_zps86dec984.jpg


ABSTRACT
An electrode assembly is formed by respectively overlaying a sheet cathode 1, a sheet separator 3 and a double-sided sheet anode 8 to form a stacked structure 10, and subjecting the stacked structure to multiple folds, wherein the initial fold comprises folding the cathode in half around the double-sided anode so as to surround the respective upper and lower active anode surfaces thereof. The multiple folds may comprise one or more subsequent parallel folds made with the fold line D-D extending perpendicular to the original length of the stacked structure such that its overall length is halved at each fold. A pouch battery comprising said electrode assembly has improved safety and performance characteristics. The pouch battery construction has especial application to lithium primary batteries.

New

http://i337.photobucket.com/albums/n385/motidog/battnewart1_zpsc029a0df.jpg

http://i337.photobucket.com/albums/n385/motidog/battnewart2_zpsb00235be.jpg

http://i337.photobucket.com/albums/n385/motidog/battnewart3_zps2b55c8ba.jpg

http://i337.photobucket.com/albums/n385/motidog/battnewart4_zpsb2fe630b.jpg

[Lyman]

Fold at separator 3 is the mechanical and heat management weak link, imo. And line "D" where the stack "returns" on itself. (10).

Thank you Machaca.

Edit.....The "POUCH" concept is N/A on GSYUASA, as the container is likely ("rigid") polypropylene. Note in the CT scan of the failure, the more deformed batteries tend to mimic what should be, imho, the correct "shape", a cylinder.

The weaker "sides" deflect the most, the "corners" very little, and the "ends" very little, as expected.

[Machaca]

Ly[ing]man:

it is not guesswork. It is based on knowledge I have researched

Kevlar and Carbon fiber (sic), are not stable in these temperatures, and off gas


Absolutely beyond belief. Aramid and CF don't burn!

You seem hell bent on emulating your namesake, Lyman Gilmore (http://www.flyingmachines.org/gilmore.html).

[Lyman]

I did not say they burned.

I cannot imagine why you are so incensed at my presence. If you ask, i will leave.

[RR_NDB]

Hi,

1) From NTSB briefiing: APU stops if it´s battery fails. :confused::confused::confused:

I don´t understand why APU stops if it´s yet running (and generating power)

I watched the video and would like a confirmation. (not so sure) :confused:

2) Any mention on cell # 6 voltage when shorts initiated BOS event? :confused:

This info was lost? (shorts could resulted from improper cell voltage)

:confused:

PS

One month after BOS event i would expect more info.

[USMCProbe]

Charred to a crisp: New pictures show how full extent of damage to burnt Dreamliner batteries which prompted emergency landing | Mail Online (http://www.dailymail.co.uk/news/article-2273840/Charred-crisp-New-pictures-extent-damage-burnt-Dreamliner-batteries-prompted-emergency-landing.html?ito=feeds-newsxml#axzz2KHl1iyxf)

I found this just now. If the link works, and you scroll down, you will see a CT scan of the ANA battery, which shows different damage, at least to my eyes, than the JAL battery.

There is a CT scan of the battery. It clearly shows a damage gradient, starting at one end, and the other in is far less damaged.

To me this makes the investigation even more difficult. On the JAL battery, I did not see a single pattern of damage. i saw at least 6 cells, all being damaged in their own separate events, and finally one shorted and entered thermal runaway causing the fire.

The ANA damage shows heat damage radiating from one end of the box to the other. The last two cells at the end show little damage.

The investigators and Boeing really have their work cut out of themselves. To me it looks like two different failures.

[USMCProbe]

My opinion.

ANA battery:

One battery entered thermal runaway, causing heat damage to the others.
causes:

A single defective/mishandled/damaged cell.
Bad battery charger/BMS


JAL battery:

Most of the battery was overcharged. One cell finally let go and shorted. Firemen put out the fire before too much heat damage to adjacent cells.
causes:

Bad battery charger/BMS
Aircraft electrical system noise/interferance/bonding caused overcharging.

The only common denominator is the battery charger/BMS. The two batteries, to me, look like they had two completely separate failure modes.

[fizz57]

Lyman,
While playing armchair engineer is great fun, I am sure Yuasa has a lot of very bright boys and girls who do this for a living and have a level of experience and expertise in the subject you and I can never aspire to. I am quite confident that the cell design and testing is top notch - dare I say on this forum, from my personal experience even if in another area, more so than they would be from any US manufacturer - and that the cells will not cook off if operated within their specified envelope.

Likewise, designing electronic circuits to meet certain current and voltage targets is almost a trivial matter these days and I would not look for any design problems in either the balancing units or the charger - with a caveat on the charger in that it apparently implements a novel charging algorithm. I'm confident that the electronics faithfully applies that algorithm, but how good is the algorithm? "Novel" does not exactly square with "well known".

What it boils down to then is the system integration aspects. Despite the complexity of the individual items, it really is no different from ensuring that a bolt or rivet isn't stressed beyond its specified limits - either that or specify a better rivet. The key factor here is whether the aircraft system as a whole - the one great unknown before the aircraft started flying, since it too is "novel" - is respecting the specifications provided to the manufacturers of the various components.

Of course the investigative bodies have to take things step by step and rule out the more obvious culprits first. My reading of the reports to date is that this has been more or less done with the batteries and electronics. Leaving....?

[USMCProbe]

Fizz57

I could not agree more about Yuasa and would add the same comment about ANA and JAL as operators. I have friends that used to work for both. There may be some other airlines in the world that might equal their fanatical attention to detail concerning maintenance. Maybe. There are none better. This fact also reduces a lot of the uncertainty of how maintenance procedures were followed. i would expect they were followed nearly perfectly, and to the letter.

[FullWings]

Mildly off-topic but the linked report from the Daily Mail above was actually a pretty good piece of factual journalism, with a lot of material brought together plus some photos I hadn't seen before. Credit where credit is due.

[pax2908]

Pic#4 from dailymail, shows a good battery with what appears to be an insulating cover (Teflon perhaps?) - I am wondering if that is a temporary protection (against dropping tools etc. before closing the blue box) or on the contrary it is to be installed permanently?

[cockney steve]

@ Turin...Yes, I understand that in an emergency, you MIGHT want to pull the last dregs out of the MAIN battery....but isn't that why it carries 2 apparently identical units?
Even allowing for the extra cost of certifying these units, they really don't come into the realms of "disposable"...at the price, I suggest that , presently,(grounding excepted) the saving on fuel and space has been wiped out several-fold by the sheer cost of these constant swap-outs

At a couple of thousand dollars each (still a lot of jet-fuel) I'd go along with it.

BUT they're tens of thousands of dollars a pop and at that price, if I were a "punter" I.E. a Boeing customer, I'd expect my Lithium batteries to be effectively managed to give me COST-EFFECTIVE Emergency power
It's not beyond the wit of smart engineers to design a proper, effective battery-management system,possibly with automatic sensing to accass that final, destructive reserve of energy.


It hasn't been done and I'd imagine the owners of these White Elephants feel well and truly shafted......save 20% on fuel, but spend multiple times that on batteries....free Russian Roulette every time your pilots switch on....will it work or will it burn?.......Yea! brilliant sales-pitch....NOT.

I'm with the majority of the last few posters.....faulty management...both in Boeing and in the Battery-system.

I've been saying it all along,- modellers have been using lithium cells for a long time now, they have fires, cell-failures and crashes...but you have to be careful playing with a 2-metre diameter flying scythe and I'm certain the lithium cells have had a lot harder use, with a far longer time between failures than the Thales item.
These modellers are NOT professionals, but they understand the care of their motive-power and subject them to very heavy currents-by the nature of R C helicopters, EVERY cycle is using the maximum safe capacity.

If they can do it,as hobbyists, why can't the might of Boeing, Thales and Securaplane , manage a "floating " emergency battery and an APU starter-battery. Even making the (probably wrong) assumption that the APU is used at every start to give start power for the main engines, there's still the pushback, engine -warm-up and taxiing times for the APU battery to recharge.

To suggest that it's not possible to operate this battery well within it's safe operating parameters is codswallop.

defective management (human and charging/monitoring. :8)

[syseng68k]

USMCProbe:

Have seen a fair amount of Japanese electronics from the inside and while some
of the design can seem a little laboured, the attention to detail was second to none.
Might have slipped a bit during the past few years, but still pretty good.
It's going that extra mile that differentiates world class from ho-hum products, imo.

In some ways ironic, but the original Japanese quality program was started by an
American just after WWII. Now they export the ideas back to us...

[Speed of Sound]

Pic#4 from dailymail, shows a good battery with what appears to be an insulating cover (Teflon perhaps?) - I am wondering if that is a temporary protection (against dropping tools etc. before closing the blue box) or on the contrary it is to be installed permanently?

Given that it doesn't cover the most delicate part of the system (the PCBs and multi-pin connectors) but does cover the battery terminals I would suggest that this insulation is installed permanently to prevent any shorting of the exposed battery terminals, particularly from damage caused to the fairly thin (conducting) case lid less than 1cm above them.

save 20% on fuel, but spend multiple times that on batteries....

I very much doubt that ANY customer will have paid the estimated $66,000 replacement cost for any of these batteries unless it can be proved that the battery was rendered u/s by customer mishandling. :)

[syseng68k]

Speed of Sound:

Didn't someone else mention $12k as being the actual cost ?.

I would have thought that there would be an exchange program for such an item, as
they are too expensive just to scrap because of a eg: battery low diagnostic message.

Edit: How do I post an image here if the box lower left says I can't post
attachments ?.

Have a block diagram / schematic and description to post...

[green granite]

syseng68k see:

http://www.pprune.org/spectators-balcony-spotters-corner/203481-image-posting-pprune-guide.html

[Speed of Sound]

I would have thought that there would be an exchange program for such an item, as they are too expensive just to scrap because of a eg: battery low diagnostic message.

I agree, although after a certain number of 'returns' I suspect Boeing/Thales/Yuasa would want to take a good look at these batteries rather than have them taken apart for reconditioning and put back into service.

I'd love to know the proportion of these replacements made to the 'APU' as opposed to the 'main'. If it is heavily weighted towards one or the other, that would be a big clue as to what was happening. Even if it was 50/50 it would help as that points towards a 'battery/charging' problem rather than a 'load/operation' problem.

[syseng68k]

green granite:

Thanks for that. The confusion was over the description in the faq section, which
said something about uploading images via the attachment process. Photobucket it
is then.

If it no longer works, then perhaps the faq should say so ?...

[syseng68k]

Hi,

Here's a quick block diagram of all the major parts and their connections for the
battery subsystem. Info from what we know already and what seems to make sense.

http://i775.photobucket.com/albums/yy37/NikonFtn/787/BatterySystem-787-2-m_zpseca59dee.jpg

Going from left to right:

External comms datalink:
Provides external comms access to the battery subsystem,
for control and status purposes from other a/c systems.

Charger & Control:
Manages the overall subsystem and has several functions:
Conditions input power to charge the battery.
Monitors the charge and discharge processes to keep
battery operation within safe limits.
Records normal and abnormal operation and events.
Provides a command set for control and status from
external systems.
Has extensive continuous built in test functions.

Control, Status and Heartbeat datalink:
Communication between charger and Battery Management System
Detects failure of communication between charger and BMS.

Battery Management System, BMS:
Measures each cell's voltage and temperature.
Balances cell voltages in relation to each other.
Communicates with the charger to report cell voltage,
temperature, normal and abnormal conditions.
Has it's own built in test functions.

Cell Voltage Measurement and Cell Balancing, a-i:
Measures each cell's voltage
Balances each cell's voltage

Temperature Sensors, 1-8:
Individual sensor mounted on each cell to provide cell
temperature measurement.

8 Cells:
4 volts nominal, 75 ampere hours each.

Contactor / Relay:
Provides electrical isolation for the series string of cells.

For the 787 system, some of above is guesswork, but is what I would
consider a minimum set of functionality for such a system. It's only
a back of envelope description though and a bare bones example.

Anyway, feel free to tear it apart, criticise, whatever...


PS: Posting images: they changed the interfaces on Photobucket, but got there
eventually :\

http://s775.beta.photobucket.com/user/NikonFtn/medi/787/BatterySystem-787-2-m_zpseca59dee.jpg.html




http://s775.beta.photobucket.com/user/NikonFtn/medi/787/BatterySystem-787-2-m_zpseca59dee.jpg.html

[Speed of Sound]

Thanks for that.

Does anyone know where the temperature sensors are situated? The only pics of the undamaged batteries I have seen have the insulator cover over the connections and I can't see where the sensor wires terminate on the damaged batteries.

[syseng68k]

Speed of Sound:

We don't have that info. Ideally a single sensor per cell, otherwise rapid temperature
rise in a single cell may not be seen in time to shut the system down...

[kilomikedelta]

SpeedOfSound, Posts #142 and #158 of this thread show the monitor connections although I don't see anything going to a temperature sensor.

[Speed of Sound]

Thanks for that.

Either my eyes are going or the resolution isn't good enough to see exactly where each sensor wire is teminated at the battery end. I may be wrong but they all seem to be connected to cell terminals or shunts including a number that seem to be connected to 'bits of metal' which are at the same potential! :confused:

[TURIN]

Cockney Steve,

Turin...Yes, I understand that in an emergency, you MIGHT want to pull the last dregs out of the MAIN battery....but isn't that why it carries 2 apparently identical units?



No, the APU and Main batteries perform completely different and seperate functions. You cannot use power from the Main Battery to start the APU anymore than you can use the APU battery to power the brakes unless you physically disconnect them and swap their positions. Do-able on the line to get the a/c back home but not a switchable feature from the flightdeck.

Even allowing for the extra cost of certifying these units, they really don't come into the realms of "disposable"....


In the event of an emergency they will be.

Normal ops they shouldn't be.


BUT they're tens of thousands of dollars a pop and at that price, if I were a "punter" I.E. a Boeing customer, I'd expect my Lithium batteries to be effectively managed to give me COST-EFFECTIVE Emergency power
It's not beyond the wit of smart engineers to design a proper, effective battery-management system,possibly with automatic sensing to access that final, destructive reserve of energy.

Absolutely. :ok:

....If they can do it,as hobbyists, why can't the might of Boeing, Thales and Securaplane , manage a "floating " emergency battery and an APU starter-battery. Even making the (probably wrong) assumption that the APU is used at every start to give start power for the main engines, there's still the pushback, engine -warm-up and taxiing times for the APU battery to recharge.


Assuming the APU battery was used to start the APU of course, which during normal turnround ops it won't be as ground power will be attached.

[rottenray]

Mildly off-topic but the linked report from the Daily Mail above was actually a pretty good piece of factual journalism, with a lot of material brought together plus some photos I hadn't seen before. Credit where credit is due.

OMG U R SO RITE!

Seriously, ALL of the images in that "article" are available elsewhere, with far less "journalistic license" surrounding their publication.

[StinkyMonkey]

I've been led to believe that the A350 is not likely to have the same problems with it's Lithium-Ion batteries as Boeing due to a difference in the design, and consequently smaller batteries will be used.

Can anyone familiar with the A350 development verify/deny/enlighten?

[FullWings]

Seriously, ALL of the images in that "article" are available elsewhere, with far less "journalistic license" surrounding their publication.
I think you'll find that applies to almost all news media today, in that it's bought/fed from Reuters, UPI, etc. Most of the aviation related material in cases like this comes from sources like the NTSB & JTSB.

One issue that crops up very regularly in PPRuNe is the standard of reporting when it comes to anything aviation related, especially incidents or accidents. If you don't live in the UK, maybe it doesn't surprise you when a tabloid newspaper produces a largely factual report on what (to the general public, at least) is a fairly technical issue. We who inhabit this small, damp island have to re-read it several times to confirm that it doesn't mention politicians' misdemeanours, football or breasts in the narrative.

Now back to batteries...

[saptzae]

@syseng68k - #570

You can't use same connection for monitoring and balancing, as the balancing current would introduce substantial measurement errors. Thus, there must be two separate pairs of wires per cell, one for monitoring and one for balancing.

Existing batteries show no indication of per cell temperature monitoring. Per cell temperature monitoring accomplishes nothing as the lag would be seconds.

An infrared camera may be of interest though, as long as it could detect an cell-internal arc withing a millisecond or so. I have no experience with infrared and don't know whether feasible.

IMHO, there will be at most a few milliseconds available to shut charging down after a cell short, to prevent damage to other cells.

Most important is to quickly detect a cell short (via voltage) transients and disable the charger. When in doubt, don't charge!

I read that some of the small standard cells have a disconnect feature on pressure rise. Pressure monitoring may also be of interest?

[Speed of Sound]

I have taken this pic from the NTSB Powerpoint presentation which is the highest resolution image I can find of the monitoring connections to the individual cells.

No obvious temperature sensor connections although the chewing gum/cotton wool over the shunt between the middle two cells on the LHS of the array looks as though it could be hiding something although it is probably just a mirror of the connection on the shunt of the RHS.

Ybat787_zpsff032c0d.jpg Photo by SoS57 | Photobucket (http://s1280.beta.photobucket.com/user/SoS57/media/Ybat787_zpsff032c0d.jpg.html?sort=3&o=0)

[Speed of Sound]

http://i1280.photobucket.com/albums/a481/SoS57/Ybat787_zpsff032c0d.jpg

[syseng68k]

saptzae:

It was just intended to be a block diagram to show the major components and
their interaction. I can redraw to show all the wires, but there wasn't
enough space between the cells on the original sketch.

From what we know already, the 787 battery does have separate circuits
for measurement & balancing. Though i'm not advocating it, it is possible
combine both functions by time sharing a single wire. ie: Charge / balance for a
period, then disconnect and measure for a period. Many modern lead acid
chargers work in exactly that way.

We have to agree to differ on the temp sensing . A single cell's temp
gradient would be easier to detect if the sensor were at the cell, rather
than several inches away at the other side of the case. As the temp sensor
is part of an overall feedback loop controlling charge current, the closer
to the cell being monitored, the less phase lag there is in the loop, thus
providing a faster overall response. Ideally, it would be embedded in the
internal folds of the cells during production, but that may be asking too
much.

As for the transient detection, that could be done by sensing cell voltage
dv/dt, either using a fast a/d converter, or much simpler, an analog
differentiator feeding a limit comparator, which then generates an interrupt
to the bms processor. I know it might be more elegant to use an a/d, but it's
not a no cost option as you not only need the fast a/d, but all the software
to drive it as well. Not difficult overall, but who knows what's on those bms
boards already.

If the temp sensor is built into the cell, then why not a pressure sensor as
well ?, though it would increase the cost considerably. Still, for a new
application such as this, perhaps extreme belt and braces will be the only
way to satisfy the regulators until more in service experience is gained...

[RR_NDB]

Hi,

"Fault Tolerance and Graceful Degradation" are essential characteristics of good Systems.

An aircraft to perform this must rely on adequate parts.

I question the use of Li Ion batteries as MAIN and APU with the current "aviation industry conditions". (including Certification)

IMHO we still lack SEVERAL IMPORTANT pre-requisites to use these batteries for above mentioned applications in airliners.

The pre-requisites cover ALL issues capable to generate (BIG) problems ranging from technical to organizational aspects.

If EADS is questioning and considering alternate solutions for A350 i think they are correct.

We engineers like "hi performance" parts in our design.

But, we must question everything prior to mass producing.

[pax2908]

Well, the full-size picture (post 581) seems to show some of the wires in the harness being too short and under tension (e.g. one near the upper right corner) - a priori I am not too impressed by the quality of this assembly.

[Alison747]

An observation based on the photograph posted above by Speed of Sound:

The central two connecting bus-bars each have two "connections", compared to one for each of the other intermediate bus-bars - one of these "connections" is under the white mass.
I notice that one of the "connections" to each bus-bar appears to have thicker wire (the ones to the centre of the bus-bar). Is it possible that these are two-wire connections to something like a thermocouple?
This might be one form of temperature sensing, but not really enough to give comfort in the high level of monitoring.

[Speed of Sound]

Well spotted although as you say, this will only really monitor the air temperature in the casing rather than individual 'hot' cells.

http://i1280.photobucket.com/albums/a481/SoS57/Ybat787b_zpsdbe696f3.jpg

[green granite]

The thing I notice is that the connectors for most of the wires seem to be push on 'spade' type connectors, which I wouldn't have dreamt of using for mission critical set-ups because of their inexplicable tendency to become loose for no apparent reason. (it may be that I'm interpreting the image wrongly)

[Ian W]

GreenGranite,
The connectors all seem to have crosshead screw atttachments. Whether there is a 'spade' or circular connecting lug cannot be seen.


On a more general point right at the beginning of this thread Machaca posted that:

Securaplane has developed a method for accurately detecting the inflection point which has eluded battery experts for years and is critical in reducing an overcharge condition. This patented method of charging ensures that the battery receives the optimum amount of charge for all temperature conditions combined with various battery states of charge.

This raises questions first about the accuracy of the algorithm for forecasting the inflection point. But also that the algorithm may rely on inputs of 'all temperature conditions' which may not actually be available in that battery pack.

[EEngr]

I notice that one of the "connections" to each bus-bar appears to have thicker wire (the ones to the centre of the bus-bar). Is it possible that these are two-wire connections to something like a thermocouple?Not really. Go back to SoS' original photo and look at those busbar connections. The thicker section is a piece of sleeving. You can see the end of it under the zip tie and the single wire coming out.

Zip ties. Not used much in my day. We preferred cable lacing: Cable lacing - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Cable_lacing)

Some of those wires appear to be pulled pretty tight as well.

[saptzae]

@syseng68k

Balancing performs discharge only < 0.05C (my estimate). Charging is serial at up to 1C. Multiplexing charger with Li cells would rely on assumptions on peak cell voltage. Extra connections to same terminal will also help with detecting wire breakage.

I like the pressure sensor idea, it would be very sensitive detecting arcing inside a cell. Actually, silicon pressure sensors have temperature sensors built in for calibration against temperature variations :).

@Alison747
There may be a temperature sensor under the white mass. There is no indication of per cell temperature sensors.

@EEngr
Concur, wire terminations are with heat-shrink tube and are tied tight to increase vibration resistance.

@Ian
IMHO circular lugs used.

I pointed the securaplane battery patent out here:
http://www.pprune.org/tech-log/505695-787-batteries-chargers.html#post7645076

It is one of those patents one gets to get a patent for making life harder for the competition to sue one. Well, and a little for marketing hype too. As to its merit, inflection, prediction, assumption is IMHO a demerit.

Guess we will learn more BMU details from the NTSB report.

[mm43]

I note there has been extensive discussion surrounding the apparent lack of temperature sensing for each of the 8 series cells in these battery packs.

I mentioned many posts ago the need in the manufacturing process to match cells for both "impedance" and "temperature". Each is relative to the other, so it is possible to deduce during the charging cycle (probably pulsed DC) the impedance of each cell under charge and by using a "look up table" determine accurately the related cell temperature.

No need for any more wires/sensors.:cool:

[saptzae]

There is no need for everyone developing their own square wheel battery.

There already is cooperation in computer and electronics technology to set standards, be it software like Linux, the W3C or Wifi or OpenGL.

I suggest that all air-framers set up a battery group or consortium to further develop the technology for the benefit of all. It would substantially cut cost and improve quality.

[saptzae]

@mm43
A match over time would be assumed. Assumption is the mother of all failure.

[grebllaw123d]

saptzae,

You wrote:
There may be a temperature sensor under the white mass

Could well be!

Look at the white mass in post#581 and compare the position of this mass with the position of some light grey stuff in the picture of the damaged battery in post#1.
But more important: Look at the picture of an undamaged battery in post#193 in the thread "ANA 787 makes emergency landing due battery fire warning"
You clearly see a white box attached to the thicker wire at a position corresponding to the position of the stuff/mass mentioned above.

brgds

[RR_NDB]

Hi,

Saptzae @ # 592

This cooperation would be useful not just for aviation.

This idea brings Synergy to an important element practically all designs require: Electric energy storage.

Aspects like safety, management, monitoring, interface to Systems (data), etc. would be addressed with common interests.

Apologize not participating more closely to the technical discussions. The idea to have pressure sensors in each cell (+ temp.) would provide means to safer operation.

The charger i am working has series (1 C) for high current and parallel (< 0,05 C) for low current. And NO SOFTWARE for cell voltage management. Other details will discuss by PM. Mulling a patent app for.

[mm43]

@saptzae
A match over time would be assumed. Assumption is the mother of all failure.Well, the discussion is about just that!

[RR_NDB]

Hi,

New batteries:

1) Maintenance free: Dozens had to be replaced prematurely
2) High MTBF: Dozens failed and 2 grounded the fleet in ~ 100,000 hours
3) Heat (cell) is not an issue: Thermal runaway created smoke and fire.
4) Safe to be located in EE bays:
In one case Logan firecrews
spent more than one hour
to control a fire. In TAK the
smoke was visible by ATC. A
non designed fuse (ground
wire) opened and probably
saved the day. (With the
prompt landing.)
5) Algorithms are capable even
to "avoid" individual cell
temperature monitoring
probes: A shorted cell
triggered a thermal
runaway. (BOS) A super
heated cell (# 3) led to a
short circuit of 12 V to
battery case as mentioned
(model) in an earlier post.

Other assumptions were made...

[cockney steve]

[QUOTE][We who inhabit this small, damp island have to re-read it several times to confirm that it doesn't mention politicians' misdemeanours, football or breasts in the narrative./QUOTE]

If you said "she's got a magnificent pair of batteries"..you couldn't volt her.:}.....sorry, couldn't resist, I blame Slasher's influence.


BACK TO BATTERIES!
@syseng...The diagram you post is very enlightening.What really jumps out at me, is the fact that this battery-pack would appear to be connected straight onto a "dirty" bus via a contactor....No filtering,no diode-protection, so the charging/monitoring circuits are in parallel woth the battery......no series protection whatsoever to protect the cells against transients ,or ,indeed, exccessive voltage on the bus....Unless i'm really thick and missing something blindingly obvious, that there's the elephant in the room.
@ Turin, yes, I understand that the electronics battery cannot be used to start the APU...but unless the RAT is defective as well (in which case "we're all doomed Captain" ) it should deploy and be producing well before the "safe " discharge level is reached on either battery.

I would think that, if the emergency was that dire that ALL power supplies were gone except a glorified car-battery (OK, a very expensive 75Ah bespoke battery) draining that extra tiny bit of power isn't going to materially alter things....in that situation, a big red switch/button to hook the APU battery to the Avionics bus may be a better last-ditch measure...(with diode/electronic protection to prevent back-feeding if the APU battery is already frazzled.)...so, what happens if the "main" battery self-destructs before/when/during , its call to duty in this "Gimli Glider"that has 4 discrete inop generating systems simultaneously?

Agreed the monitoring wires look tight and I don't buy the Vibration theory. they appear to be standard eyelet crimps and I'd have expected a decent piece of shrink-sleeve over the end support -crimp,extending a cm.or so out along the wire insulation...can't make out if the actual core is crimped or solderedbut i'd really like to see a soldered/spot-welded connection to the busbars,instead of a scabby little self-tapper.

still not impressed after reading all these posts by real engineers who really appear to understand this subject far better than me.
Thank you all, it's a fascinating subject.

[mm43]

@RR_NDB
Heat (cell) is not an issue: Thermal runaway created smoke and fire.You can't have one without the other.

If you are meaning a spontaneous cell short, the result is still heat, and the BMS should detect a rapid change in either temperature or cell impedance.

[RR_NDB]

Hi,

mm43,

Let´s put it crystal clear:

It´s unbelievable but it seems the designers of the battery didn´t consider cell heat. NTSB model is: Short(s) generated heat and a "positive feedback" started (the so called, Thermal Runaway) leading to the destruction of the battery with other much more dangerous cosequences like FIRE.

This as i understood is the WHAT, Deborah mentioned in first briefing. It remain the WHY. We expect this in next interim and their looking to "surounding electric environment" is a logical step in the investigation. I was concerned with the no mention of cell voltages. If this data was lost (i suspect, was) the shorts could be for more than one reason. Indeed temp.(of EACH cell), voltage, impedance are intrinsically related.

[Uncle Fred]

Cockney Steve

I am sure Turin can weigh in as well but there seems to be a slight misperception about what the purpose the aircraft main battery serves in a degraded power state. Indeed if it it a race to the aerodrome the battery should last for 30 minutes to provide absolute essential power-think in this case of the captain's flight instruments. This has been pretty much the standard on every Boeing that I have flown as well as MD, Lockheed, and narrow body Airbus.

What really should be going on however, is that the battery is providing power long enough until you can climb back out of the degraded power state. This might mean the RAT starts powering the busses, the apu comes on line, or you can get a generator back. It should be just an interim power source at most.

I know you realize this but I am not sure some that are following this thread do.

Btw. I have a colleague who landed in South America on battery power only in a 767. 40 minutes on this power source. 10 more than advertised but it was drained on the rollout....close...

[USMCProbe]

I am glad to be wrong. The NTSB said both failures were caused by the same thing. I cell failed (for some reason).

The only thing I don't like in the battery is what Cockney Steve said. I want a metal contact for all those little wires. Not mechanical. Too mainy points to corrode, poor installation, etc.

[robdean]

Seattle Times:

NTSB challenges Boeing estimates of 787 battery safety (http://seattletimes.com/html/businesstechnology/2020307773_ntsb787xml.html)

Some well chosen and rather salutary quotes in the piece...

[RR_NDB]

Hi,

Question:

Airliners benefits today and will benefit in near future in using Li ion batteries?

Some facts:


When they fail you are not able to use it and sometimes the stored energy is automatically used to create fireworks inside your aircraft.
1 month after 1st 787 incident (BOS) NTSB didn´t know WHY (http://www.ntsb.gov/news/2013/130207.html) (happened)
No one could tell when Boeing 787 will return to commercial operation. The implications of this uncertainty affects thousands of professionals.
You can´t not retrieve all the energy stored. Unless you damage one or more cells. The Thales battery price is about US$ 16,000 (each)
After years of R&D, prominent high tech. aviation suppliers delivered a BAD battery damaging the Dream (liner) of a giant: Boeing (http://www.boeing.com)
Boeing is concerned and regrets: "the entire Boeing team deeply regrets the impact that recent events have had on our customers and their passengers." (http://www.boeing.com/commercial/787family/020713_statement.html)
The insurance companies are not yet able to know the costs (to be paid) but the insurance costs certainly will go higher. (http://www.insurancejournal.com/news/international/2013/01/30/279420.htm)
EADS is questioning it´s use on A350 (http://www.reuters.com/article/2013/02/08/us-airbus-batteries-idUSBRE9170HL20130208)
Better batteries are being designed but will not be available for immediate use.
A retrofit to 787 is absolutely technically feasible. The use of another battery (Ni Cd) is affordable.


Question 2: Limited test activities (http://www.boeing.com/commercial/787family/020713_statement.html) are being planned with just Li ion batteries? :confused:

[Lyman]

The NTSB has narrowed the failure down to some criteria. Internal defects are on the list, and cannot, by their nature, be monitored, or even known, until failure. They are mentioned as related to the folding of the electrode, pinching and wrinkling, and foreign object contamination.

This report is not a new revelation. This failure is well known in the industry, see Failure Analysis Associates, Exponent evaluation.

NTSB may appear to be discovering this problem just now. Wrong, it was on their list, it was on the list prior to the wording of the FAA special circumstances.

Try to avoid the propaganda that somehow something mysterious is happening.
Any Drama is Public Relations.

As has been said here before, this is "Mature Technology". That is true, but "Mature" is not a synonym for "Safe in Commercial Aviation".

As to Boeing writing the regs. Let's see. I am in a spelling Bee, as a contestant.

May I submit the word which I will be required to Spell?

[RR_NDB]

Hi,

syseng68k:


Negative going voltage spikes in DC bus could "turn on" diode module
(http://www.pprune.org/tech-log/505695-787-batteries-chargers-18.html#post7667727)
An analogy can be made
(http://www.pprune.org/tech-log/505695-787-batteries-chargers-18.html#post7667788)

[RR_NDB]

Hi,

Low MTTR:

"...the top three reasons for Boeing returning batteries” as batteries running down, being improperly disconnected, or exceeding their expiration date."
(http://seattletimes.com/html/businesstechnology/2020241385_787deadbatteriesxml.html)

A battery that’s left on with no other power source, Gunter said, “will deep discharge (and) cannot be recharged or reused.”:{

And one that’s improperly disconnected, she added, “trips one of the protection features and renders the battery unusable.”
:{

Because lithium-ion batteries can be dangerously volatile if undercharged, as well as when overcharged, an automatic cutoff is built into the 787 batteries so that if the charge falls below 15 percent of full, the battery locks.
After some problems during trips, some years ago i opened and analyzed the 6 cell battery pack of my main laptop. The voltage span from empty to full used in that design was just one volt. IIRC 11.6 to 12.6 Volts. I decided to use an external battery for my main and spare laptops. Currently i use 12 cells, charging each one up to 4.2 volts with constant voltage monitoring. Warning me if a given cell falls below 3.3 volts during operation. Result: 10 hour plus operation. :) Ea. cell can be replaced. (18650) :ok:

[Machaca]

Lyman: The standard set by the FAA for this safety critical event is one occurrence in one Billion flight hours.


FALSE.

That standard does not apply to the battery system, as it is not critical for flight.

I urge contributors to this thread to please refrain from posting unfounded hyperbole. It does nothing to further our understanding of the technical issues at hand, bothers those professionals well versed in the industry standards, and misleads the gullible.

[USMCProbe]

Regulating agencies are always a step behind the industries that they regulate. If they were not, there would be no innovation. Banks, airplanes, whatever. I don't blame the FAA. They did the best they could with the info they had.

[RR_NDB]

Hi,

Batteries cell voltages in JA829J and JA804A were recorded? (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-39.html#post7687229)NTSB and JTSB mentioned cell voltages?

[RR_NDB]

Hi,

(http://seattletimes.com/html/businesstechnology/2020241162_787battery29xml.html?prmid=obinsource)And what about intercell spacing? (http://seattletimes.com/html/businesstechnology/2020241162_787battery29xml.html?prmid=obinsource)


http://i48.tinypic.com/2lc8njr.jpg

[saptzae]

@RR_NDB

CVR/FDR are recorders for investigative purpose.

QAR records more in detail, with maintenance in mind.

Subsystems do their own recording. Frequently, investigations looked for example at FADEC NVM.

So far, there is no hint on availability of any per cell recordings. Sensibly, the BMS would record (amongst others) things like


Event time stamp
Cell #
Cell voltage
Cell short/over voltage/under-voltage
Charger on/off
Failure notification
Breaker tripped / disconnected
Battery temperature/fire

At BOS smoke/fire was observed, but no hint on any prior battery related alert.

IMHO, NTSB based their BOS related analysis, as of 6 Feb brief, on FDR (32V, no overcharge), and on physical evidence / examination after disassembling battery and cells.

We know that 32V during a cell short will result in destruction of remaining cells. To figure it out, the following info is needed.


Battery temperature history
Per cell voltage history
Per cell voltages prior to Primary failure
BMS response to Primary failure
Battery voltage after Primary failure - Has it reduced or remained at 32V
Precise failure sequence

[Machaca]

Lyman: having been reduced from the one billion figure


FALSE. No such reduction ever took place.

Posting nonsense incorrectly extrapolated from opinions collected by journalists doesn't lead to a better understanding.

There is an immense difference between the designed failure rate requirements for flight critical systems and other systems and components.

One may opine what qualifies as such, but that doesn't make it so.

[RR_NDB]

Hi,

saptzae:

Battery temperature history
Per cell voltage history
Per cell voltages prior to Primary failure
BMS response to Primary failure
Battery voltage after Primary failure - Has it reduced or remained at 32V
Precise failure sequence (http://www.pprune.org/tech-log/505695-787-batteries-chargers-31.html#post7687328)
:ok:


But, if Investigators were with only "Per cell voltage history" like the old CVR approach (endless tape) probably they would be ready (some time ago) to deterministically say the "WHAT and WHY" in these BAD batteries that initiated the thermal runaway, GROUNDING THE 787. :{

[RR_NDB]

Hi,

saptzae:

We know that 32V during a cell short will result in destruction of remaining cells. (http://www.pprune.org/tech-log/505695-787-batteries-chargers-31.html#post7687382)

:} Yes, with a poorly designed system you even display fireworks. :{

(When a cell starts to exhibit anomalies YOU CAN IMMEDIATELY process the info and decide what to do. AFAIK the people that worked in the algorithms had this techniques available to implement a "world class" design. 787 deserved it!

:mad:

[CliveL]

I urge contributors to this thread to please refrain from posting unfounded hyperbole. It does nothing to further our understanding of the technical issues at hand, bothers those professionals well versed in the industry standards, and misleads the gullible. I couldn't agree more

:ok::ok:

[HazelNuts39]

Ether former safety board member John Goglia was misquoted by the interviewing journalist, or he would be well advised to refrain from making erroneous statements about matters he doesn't understand.

[Lyman]

HazelNuts39

I quoted the article in good faith, and will retain it in my files.

I will remove all reference to the remarks from this thread.

Your information I consider to be the gold standard, here.

Thanks for your intercession...

[RR_NDB]

Hi,

In first NTSB briefing Deborah Hersman emphasized WHAT and WHY on BOS 787 incident.

WHAT: A short circuit inside a cell.

Problem now (WHY) seems much more complex. Even impossible to conclude:

1) PCB´s probably were FUBAR

2) Cell voltage history (before and after thermal runaway) probably were lost

If this is true, the only way to recover cell voltage history would be if battery voltage was measured and recorded. (NOT THE DC bus as happens in a conventional plane) Remember that between the cells plus terminal (the right position to measure) and the bus you have a relay/contactor and a diode module (this one specific to 787, because using Li ion that only "goes to the bus" if it drop below, i estimate 30 V)

So, if the voltage at battery plus terminal of cell # 8 was not measured or recorded NTSB will have two possibilities:

1) A cell failure from a non electric reason. (process, etc.)

2) A cell failure from a cell voltage balancing failure when battery was being charged. (Series charging, IMO not the best approach)

Considering JA829J (http://www.pprune.org/www.youtube.com/watch?v=bhHpoCmNB_U) started flying few weeks before the incident, very probably no other battery was used (and replaced) in that plane. So not possible (very probably) to look to other battery used in (APU) this plane.

So i don´t expect a conclusive WHY from NTSB for this particular battery failure. Simply i cannot imagine how to conclude. (the WHY)

The fact they are going to see process (manuf., design and chargers) is an indication they had no means to find the WHY in using the shortest procedure: Looking to the smoking gun.

On the question in the Title: What concerns me most is the FAA design review. A mere change to Ni Cd could not be the only required change.

:{

[bill good]

Cell failure - multi current paths involving metal cased cells & metal battery case all resulting in further cell failures currents via earth straps bonding, heat etc. If need to stay with the same cells. Answer redesign battery case for temps above 800 degs C without metal. Material- basalt internal with kevlar external safety outer. Basalt & kevlar dividers between cells. Good for over 1600 degs C. No shorts, no ground loops, light weight.

Most batteries changed because they had been discharged too far. (ground handling?) It is most likely to be found the underlying reason for the two major failures. State of charge indications as a percentage comes to mind. If it at the present displayed as a percentage, then the low end should be recalabrated. If it is voltage it is just wrong. ( don't have how it is displayed & could not find ref in the thread.) The voltage indication of Li-Ion batteries between good & bad are too close for voltage readings anyhow. (coulomb counting for short term indicating)


Regards

[RR_NDB]

Hi,

EEngr:

The 'current spike' brings up another issue which I have found to be often overlooked. That is: the electrical loads on these batteries are not steady state DC. Particularly in the case of the APU, the starter/generator is driven by a controller that draws very high levels of ripple currents from the source.

Batteries, in addition to being an electrochemical voltage source have an equivalent AC model that (overly simplified) can be represented as a series LCR circuit at higher frequencies (tens or hundreds of kHz). If one excites such a circuit near its resonance, it is possible to generate extremely high voltages across the various internal points of this equivalent circuit.

There is the possibility that the various combinations of load ripple and battery AC impedance was not properly characterized when the initial certification analysis was done*. I imagine that subsequent flight tests will be instrumented to capture exactly this kind of data.

*Back in my days at Boeing, I was involved with the 767 static inverter and its adaption to the 747-400. Initially, it had been certified to drive linear AC loads. This was because the smaller loads (typically driven by the standby AC bus) were exempt from limits on harmonic current draw. But, as it turns out, being exempt from a spec requirement doesn't meant that it shouldn't be considered. It turned out that an inverter rated at 1kVA was only capable of delivering about 400 VA to the connected loads before the voltage waveform became so flat-topped that it's output fell out of spec. This new 'all electric' airplane may turn out biting some old school engineers in the a.:mad:

I am particularly interested to discuss this issue. I love Circuit theory. :8

Questions:

1) You consider the possibility of the cell voltages varying outside "safe limits" during transients that as you mentioned occur starting APU?
2) The equivalent LCR of the battery could resonate in this frequency range? (hundreds of KHz)
3) The relay/contactor could generate cell voltage unsafe transients? (opening under high load)
4) The diode module could be an extra factor? (e.g. to cell "integrity" during transients)

Why we hear the inverters noise in HF radio transmission coming from the 767? We know a given call is being made from a 767. :) EMI/EMC or just filtering issues?

[saptzae]

@RR_NDB

As an alternative path to inducing cell damage, short duration load transients would be tolerable, as long as cells do not drop below minimum voltage.

The APU starter generator is inverter driven. Unlike an old fashioned DC starter motor, it will, at most, pull little more than rated current. Actual startup current will be less than rated current.

I have no data, I'd go for startup current of less than 100A rising to up to 300A. At 300A * 25V = 7.5KW into the inverter, motoring would deliver at least 6KW at the shaft.

Resonant effects can be very damaging, in electrical as well as mechanical systems. Back in the 1920s and 1930s, torsional vibration destroyed plenty of crank shafts and gear boxes of the new twin row radial engines, before it was understood through testing, and well prior to developing the maths behind it.

Resonant currents on the bus would be an ineresting scenario. I experienced load dependent oscillation during charger development.

[saptzae]

@Lyman

Some here, including myself, like to focus on technical discussion, to understand what really happened.

IMHO, R&N is the better place for "high-level" discussion of great political and strategic significance.

[Lyman]

Yes, of course.

I think the battery enclosure is certainly a technical issue, as are the certifications the FAA applied to the technology as BOEING interpreted it.

from the photos of the JAL accident, I note some serious charring of the (composite) decking underneath the APU Batt's install site. So that suggests an improvement in separation, battery case from a/c structure might be warranted as well as the isolation of the eight cells within the enclosure. Perhaps an inerting tray, of some non conductive material, perhaps a ceramic.

The space within the E/E bay appears sufficiently large to accomodate a reasonable increase in the space required for an upgraded battery system. Problems of pressure cycling, cell casing, gas production, etc. certainly would impact the discussion?

[Frequent Traveller]

If we make the assumption that the chemistry of Lithium-ion batteries is as yet UNSUFFICIENTLY KNOWN ? let me prompt that - food for thought, possibly ? - the electro-chemical reaction liberating free electrons (electrical current) in those Japanese (YUASA) batteries has TWO ALTERNATIVE writings, ONE (standard, well-known, basic) upon which the battery control system engineering has been conceived (and may correctly serve to govern/control/protect) plus ONE OTHER electrochemical ALTERNATIVE REACTION ? with a DIFFERENT WRITING, liberating a much greater number of free electrons in a CHAIN REACTION producing a discharge current of much greater intensity (amperage) for which the present battery protection system has NOT been designed to cope with and of which the Battery Maker is UNAWARE, the inherent assumption here being that the OCCURRANCE of the alternative electro-chemical reaction would be commanded by Quantum-Mechanical principles (RANDOM basis ?) under certain (very particular) catalytic conditions (hypothetically : eg some mechanical vibration of the anode/cathode and electrolyte at given frequencies or otherwise, in presence of PPM traces of catalytic impurities in said anode/cathode/electrolyte ?)
Engineering at Brown University (http://www.brown.edu/Departments/Engineering/Labs/Gudurulab/Research.htm)
(see papers n° 1 and n° 2 indicating that Lithium-ion battery technology is still at the Research & Development stage in 2013, five years after the 787's airworthiness certification ?) :(

[syseng68k]

RR_NDB, 606

Away for a few more days - work still must be done :8.

Re: The red herring comment, spikes on the bus are way down the list
of possible suspects imho. Although the data sheets don't provide an
ac model for the cell, one would expect the self capacitance to be
very high, the self inductance to be very low, and the esr to be in
the fractions of a milliohm range. All this would provide very good
damping for any transients on the bus. It's still good to discuss it
though, even if everyone doesn't agree - it would be pretty boring
and unproductive if we all did.

For me, it's still down to battery management, at the risk of banging
on about it. Either charge or load related. I still don't see any reason
why those batteries caught fire and the if bms was doing it's job right, it
should have disconnected the battery at the first sign of trouble, which
it should have been able to detect. No excuses please.

Just like the unprotected electronics and harness in the enclosure,
perhaps too many (arrogant ?) assumptions made during the bms design
stage...

[Lyman]

Hi Chris.

I hope not a stupid question..... Could the battery problem be system related insofar as the battery itself increases its resistance internally?

NTSB is looking at manufacture defects, leading to internal shorting, (on a "microscopic basis"). If this is happening, is there some point at which the battery cannot be controlled externally?

The NTSB isolated the #6 cell as the source of the initial runaway. Working backward, where do you see the failure as initiating? I know it is a general question, but could you contrast physical separation cell/cell, and circuit isolation?

Are these two problems independent? We don't see the ability to separate each cell from the circuit, do we?

[syseng68k]

saptzae, #623

Resonant currents on the bus would be an interesting scenario. I experienced
load dependent oscillation during charger development.
Had a the same problem with a one off rotary inverter speed and voltage
control for a lab power supply. With any mechanical devoce in the loop, it
can be quite difficult to model / analyse from basic servo theory and there's usually
some hand tweaking of the lead / lag networks to get it right, especially
if your maths is a bit rusty, like mine. My excuse was / is that too many years
of software have partially dissolved the higher facilities, but ymmv :).

Resonant currents might be a possibility, but resonant with what ?. The apu
starter conditions might be the worst case, but the pwm driver for the
starter motor must be well filtered to prevent interference with radio and
other sensitive avionics. Any transient effects will be in the 10's or
hundreds of milliseconds range, not microseconds and you can't have those
effects without considerable inductance in the line. Transmission line theory
applies and all that...

[MurphyWasRight]

Any transient effects will be in the 10's or
hundreds of milliseconds range, not microseconds and you can't have those effects without considerable inductance in the line.


One can get a a "resonant/positive feedback" effect if a controller reacts to resistance changes (temp rise from current flow) with a time lag that aproximates the conductors thermal time constant.

The above time constants sound about right for large conductors, especially if one pressumes a slightly faulty connection in the path.

Not knowing the details it is hard to say if this is likely but I do know of instances in other fields where thermal "tails" have caught designers by surprise.

[syseng68k]

Lyman:

The NTSB isolated the #6 cell as the source of the initial runaway. Working
backward, where do you see the failure as initiating?
Imho, the precursor to the initial runaway should have been detected by the bms
as an excessive temp rise or temperature gradient in that cell. If each cell's
temperature is being monitored, detection of an overtemperature condition
should have been part of the process, just as temperature monitoring is critical
to limit charge current to a safe value.

I know there's been some discussion about whether a sensor on each cell would
be fast enough to detect the rise, but the cells do have thermal mass and
unless a short circuit or very high charge current were applied, the temp
rise over time would be such that a sensor should detect it. As the cells have
electrolyte, the thermal resistance from cell core to case should be fairly low.
Temp rise timescales might be in the low minutes under normal operating
conditions. Plenty long enough to be detected by a sensor on the cell casing,
but maybe not so if that sensor were several inches / 10's cm away on the
enclosure wall...

[EEngr]

RR_NDB (http://www.pprune.org/members/349485-rr_ndb)

1) You consider the possibility of the cell voltages varying outside "safe limits" during transients that as you mentioned occur starting APU?This might be more of a steady state phenomena. This APU is an AC device, driven by a variable frequency drive (an three phase inverter). Although there is some input filtering on such units, they do draw continuous ripple current on top of the DC supply. And this ripple current will change in magnitude and frequency as the APU starter accellerates.


2) The equivalent LCR of the battery could resonate in this frequency range? (hundreds of KHz)It is possible. Some analysis and tests could be done to characterize the batteries' AC response. An LCR circuit might be an over simplification of what is actually going on. For the real RF engineers, it could be more like a lossy transmission line, with standing waves along the battery ribbon and the resulting higher voltages at these nodes. But for simple understanding, the lumped model (as discrete components) will suffice. Here is some more info:

LC circuit - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/LC_circuit#Series_LC_circuit)

Two damage modes might be possible: First, the voltage across a series LC circuit at resonance is at a peak across the L and C (but out of phase). The C here is the capacitor created by the battery plates and seperator. If this rises above the designed insulation level of that insulator (3.7 V plus some margin of error), it could punch through and initiate a short in the cell. The other possible mechanism is electrolyte heating due to losses caused by the r.f. voltages. Some capacitors are noted for having high internal losses (dissipation factor for the EEs) and, as a result heat up (and sometimes explode :mad:) when driven with a ripple current/frequency over their rating. Although the total voltages don't exceed the insulation's capability, hot spots can be generated.

3) The relay/contactor could generate cell voltage unsafe transients? (opening under high load)
4) The diode module could be an extra factor? (e.g. to cell "integrity" during transients) These are possible as well, creating some high voltages due to the "inductive kick" experienced when switching high currents.

This is all guessing on my part. But given the design and certification program of the 787, it is likely that the consequences of load interaction with the battery were not completely tested. When the battery system was being developed, no actual loads (with their AC rippe) were available yet to characterize their effects. Hence the planned flight testing program.

The fortunate thing about these effects is that; should they prove to be the root cause of failres, there are some simple and inexpensive filtering techniques that can be adapted to the battery/load circuits to mitigate them.

[Lyman]

Thank you Chris...

Where I have wanted to go is to Thermal. From your background, would you have in mind discrete heat signatures relative to Chemical decomposition as opposed to resistance generated heat events?

My question has to do with my perhaps faulty image of electrical resistance induced heat, and chemical, and chem/elec combinations?

Would the heat generated by internal fault be more local, and suggest the need
for multiple samples in the cell interior?

Does resistance produced by overcharging lend itself to more local sensors?

Like at the strap, or connectors?

If this technology is allowed into the future, what do you see as the difficulties in monitoring for these internal problems?

very curious....Thank you for your patience, and time.

[syseng68k]

saptzae:

So far, there is no hint on availability of any per cell recordings. Sensibly,
the BMS would record (amongst others) things like

Event time stamp
Cell #
Cell voltage
Cell short/over voltage/under-voltage
Charger on/off
Failure notification
Breaker tripped / disconnected
Battery temperature/fire

Very much so. Something that's been bothering me for some time is the almost
obsessive concentration in the reports about the batteries, but still not a word
about the data logs for the battery subsystems. If all the above data is
being recorded, there should be a complete timeline of the events that led up
to the failure.

If they have the above, they have the reason already, unless such data is not
actually being recorded...

[Lyman]

If the certifications were met, and they were, there would be no need for such extensive monitoring.

EXCEPT in a test Programme. Boeing tested and concluded there would be no propagation cell to cell, and any cell failure, any kind, could therefore be effectively ignored.

I think the reason we have not heard about extensive monitoring in these systems is because there is none.

EG: The JAL battery likely went off line immediately when the single heat sensor recorded temperature limit. But by that time, Electrical circuitry was not a concern, because at that point, explosive expansion, flame, and smoke became the issue.

NTSB stated there were no over voltage issues. That means to me, there was a shutdown, but not due to electrical circuitry issues.

Overtemp. Likely due the construction/architecture/ageing?

IOW: The system Worked....By design. Badly.
That may soon change?

[mm43]

@Lyman,
I think the reason we have not heard about extensive monitoring in these systems is because there is none.Securaplane (http://www.securaplane.com/download/doc_download/36-lithium-battery-charger-unit),
Our new, innovative battery chargers use advanced DC to DC conversion technology, patented charging algorithms, comprehensive diagnostics and fault isolation.Mx got the info from somewhere, and knew when to change the units out.

[Lyman]

mm43

Mx got the info from somewhere, and knew when to change the units out.

Yep. Likely a red light on the panel. Doubt Mx inspected the actual battery to get the notice...

And that could be generated from those separate leads, calculating charging response against an indexed standard?

One thinks the accelerated replacement Program got accelerated straight away after the first two or three unscheduled BATT FAULT prompts.

I think the monitoring is visible on the undamaged Batts on display. Because these cells do not tolerate inclusion of foreign material in the cell itself, temperature monitoring got the short stick.I think the "White Wad" might be the only temperature sensing device?

Is there a temperature sensor that melts at a given value, say 120C that then opens up the circuit, stopping all electrical activity? A variation on a "Fusible Link"? If so, that may be the trigger for the ECAM. No current from the battery'

Didn't ANA report a drop to zero voltage concurrent with the smoke event?

:ok:

[syseng68k]

Lyman:

Where I have wanted to go is to Thermal. From your background, would you have
in mind discrete heat signatures relative to Chemical decomposition as opposed
to resistance generated heat events?
It really isn't that complicated, starting from the premise that the cell will
work as advertised if not abused. I'm not a chemist and am quite happy to let
Yuasa deal with that and overall physical construction.

The cell data sheet specifies a maximum temperature, which if exceeded may lead
to thermal runaway. It's the job of the bms to limit the temperature based on the
data sheet values, with a margin of safety. Ie: if the cell is rated at 65C, then
the bms must have a hard limit below this, say 60C. For whatever reason, the
cells should be disconnected from charge or load if that limit is exceeded. The
same applies to min and max cell voltage monitoring, which did appear to work,
judging by the number of batteries that were swapped out due to excessive
discharge...

[Lyman]

same applies to min and max cell voltage monitoring, which did appear to work, judging by the number of batteries that were swapped out due to excessive discharge

Excessive discharge, or "low voltage"? If cells were failing, wouldn't the lowered voltage show as what could be claimed as "discharge"? Wouldn't said low voltage be a "no dispatch"? Creating some real urgency?

[syseng68k]

EEngr:

This might be more of a steady state phenomena. This APU is an AC device,
driven by a variable frequency drive (an three phase inverter). Although
there is some input filtering on such units, they do draw continuous ripple
current on top of the DC supply. And this ripple current will change in
magnitude and frequency as the APU starter accellerates.
I'm skeptical, in that the ripple current on the dc line will be directly
related to the inverter o/p frequency, which will be at most, in the low
Khz and more likely the low hundreds of Hz. The input filtering must provide
effective filtering for the pwm carrier, which would be typically in the low Khz
range anyway.

Would the battery have a problem dealing with ripple in the low Khz
range ?. Such ripple would be riding on the nominal dc and wouldn't cause
transients above battery unloaded voltage. You need inductance in the line
to produce significant transients above battery nominal voltage and a few feet
of wire would only produce nanosecond level transients. Insignificant..


Some capacitors are noted for having high internal losses (dissipation
factor for the EEs) and, as a result heat up (and sometimes explode )
when driven with a ripple current/frequency over their rating. Although
the total voltages don't exceed the insulation's capability, hot spots
can be generated.
Agreed, but caps for that sort of service are designed for low esr, have
specified ripple ratings and are designed to tolerate hf / fast rise edges.
I really doubt if the cells would be subjected to anything like that high a
frequency, since there would be considerable rf radiation to other systems
as a result...

[mm43]

Lyman,
Doubt Mx inspected the actual battery to get the notice...The Securaplane battery charger carries its own diagnostic tool and records appropriate data. I suspect chargers will be located nearby each of the suspect battery packs, and according to the maker, the earlier BC-1300 series supplies the following:-

Charger faults - Fan speed, CPU Temperature, Voltage, Current, Power, Stored fault history.
Battery faults - Abnormal temperature, Temperature sensor circuit, Cell unbalance sensor unit.
LED display - Eight-character alpha-numeric.
Diagnostics - Self test, Output voltage, Output current, Operating hours, Temperatures, Power.
Time - Date, Software revision.
Charge mode - Bulk charge mode, Topping charge mode, Trickle charge mode.

The likelihood of their flagship B787 charger providing less data than above would IMHO be highly unlikely.

Supposing that the JTSB and NTSB examined the charger records straight up and found nothing untoward except the battery fail event, then it would be reasonable for them to dissect battery cells in order to deduce a reason for that failure.

[Lyman]

bonjour mm43!

Diagnostics - Self test, Output voltage, Output current, Operating hours, Temperatures, Power.


Was the BC-1300 LithIon specific? From the literature, the LithIon pack, whether pouch, prism or roll, does not tolerate intrusion into its Cathode, Separator, Anode stack. Even the slightest foreign object will cause a focal "shutdown" and compromise the useful life.

I have no doubt there are diagnostics and storage. The Battery install, however, suggests the only wiring external to the case is +/- conductors, and Ground. Would the diagnostics storage be co-located with the PCBs? Inside the case?

many thanks

[RetiredF4]

Two pictures i hadn´t seen published with side views of the cells

787 battery cell pictures (http://blogs.crikey.com.au/planetalking/wp-content/blogs.dir/10/files/2013/02/Inside-battery3.jpg)

from this site (http://blogs.crikey.com.au/planetalking/2013/02/08/dreamliner-787-hints-of-dissent-appear-off-stage/)

[kilomikedelta]

There is only one wire going into the white wad which I suspect is connected to the intercell strap like the strap to its immediate right. Having a temperature sensitive device in series with this wire (if it is indeed the temperature sensor) would be illogical.

[Lyman]

kilo It could easily be a pair, imho. The sensor would not be "connected" electrically to the strap, but affixed with adhesive. Check the image supplied by Retired F4? on the left, on top, you will see remnants of the "WhiteWad" undamaged by fire. my assumption is that it is 'fireproof' and could indeed be an insulator, cover for a temp sensor?

franzl...Those pics are from the NTSB page 7 "Thermal Damage" "page"?

This page shows the orientation incorrectly. the image on the left, has the "front" of the Battery on the left. That makes the side closest the "Right" side, not the left. The other image the same, reversed.

That is, if the orientation is observed from the "front" of the battery.

My conclusion is that the more severe damage, that on the 'right' side (the correct labelling), is also the side closest to the serious damage to the equipment in the bay to the right of the APU BATT situs. There was severe heat damage to the decking below the Battery as well. Fire damage was NOT limited to the interior of the Battery enclosure, and the fire damaged equipment outside the battery, something the Installation was required not to do, per the Lithium considerations in the FARs.

Is that the Sandilands' site?

[syseng68k]

MM43:


Charger faults - Fan speed, CPU Temperature, Voltage, Current, Power, Stored fault history.
Battery faults - Abnormal temperature, Temperature sensor circuit, Cell unbalance sensor unit.
LED display - Eight-character alpha-numeric.
Diagnostics - Self test, Output voltage, Output current, Operating hours, Temperatures, Power.
Time - Date, Software revision.
Charge mode - Bulk charge mode, Topping charge mode, Trickle charge mode.

The likelihood of their flagship B787 charger providing less data than
above would IMHO be highly unlikely.


Ideally, yes, but the devil's in the detail. It doesn't say, for example, if
temperature is sensed for each cell, nor does it say what the sample frequency
is, ie: how often data is logged and under what conditions; singly on a
significant event, or continuously in the background, much as an fdr would
during flight.

Some systems log all the data at fixed intervals or sample rates, with each data
log entry timestamped, so that faults that develop over time can be traced back
by reviewing all the records. If the charger only logs a subset of available data,
or logs at too infrequent intervals, then it's quite possible that events that
lead up to a serious failure will be missed in the log. .


Supposing that the JTSB and NTSB examined the charger records straight up and
found nothing untoward except the battery fail event, then it would be reasonable
for them to dissect battery cells in order to deduce a reason for that failure.
Possibly, but it's also possible that there's not enough data being logged in the
first place for an accurate assessment...

[HazelNuts39]

kilomikedelta: agreed

A possible location for one or more temperature sensors is the transverse 'bar' that separates cells 2 and 7 from cells 3 and 6. There are some wires going down from that bar between cells 2 and 3 near the battery case. There are also 5 or 6 wires going to a connector that is vaguely visible below the connector that connects the left half of the cell voltage harness to the rear PCB:
http://i.imgur.com/2iLmApE.jpg?1
http://i.imgur.com/TYl9cku.jpg?1

[Lyman]

HazelNuts39

It is cells 2,6 and 3,7 that are paired, transverse. According to the image above.

from RetiredF4's post

[FlightPathOBN]

Lyman, others...

The size of those wires, carrying that much amperage??? Really? Powering an aircraft?? :\

What is to bet the charging system wiring is used to heat the main cabin

If the batteries are that sensitive to differences, would not the individual wire length be of concern?

I see the bus bars, but what are those connected to?

Boeing just whored (hired)a new person to source the battery/charging aux power assemblies.

[Lyman]

The conductors at the front of the battery case looked about 8 Gauge, braided Copper.

[kilomikedelta]

Just so we're all singing from the same page in the hymn book: Cell #1 is closest to the printed circuit boards (front of case) on the left case side, cell #4 is at the the left back of the case, cell #5 is closest to the printed circuit boards in the right side of the case etc. Do we agree? The 37 monitor wires are just that. They only connect to the printed circuit boards. The output jack (J3) comprizes two ~1/4 inch diameter sockets good for ? 60 amperes for a reasonable distance. I don't see any monitor wires going between the cells below their tops.

[mm43]

Lyman - #641,
The Battery install, however, suggests the only wiring external to the case is +/- conductors, and Ground. Would the diagnostics storage be co-located with the PCBs? Inside the case? To the contrary, the charger and the battery case are connected by a multiple pin cable, and the PCB's located in the battery compartment are probably concerned with buffering bi-directional data between the units.
http://oi49.tinypic.com/23mn95e.jpg

The THALES charger above and a close-up of the J1 circular connector under examination by NTSB is below. The battery case has the complementary data connector above the battery terminal connectors.

http://oi46.tinypic.com/14vs6q8.jpg

This link will provide a large close-up (http://oi45.tinypic.com/smugdw.jpg) of the front of the JAL battery case.

My guess is that THALES is the prime contractor and Securaplane is the sub-contractor providing the charger and BMS.

@ syseng68k

I suspect from what I see, that a great deal of data is being processed between the units.

[Lyman]

kilo, did you spot the remnants of WhiteWad? Did you see my correction to the labelling on the Thermal Damage image? Right/Left transposed?

mm43. I did not see the pin coupler, the battery was too fried. Again, though, re: the BC-1300 monitor/ is it dedicated to LITHIUM Ion?

The sensing of temperature could certainly be done at the external cell casing, but I don't think any internal data could be had?

[Lyman]

mm43 are you sure the link to the Battery close up is JAL? JAL had the cover plate and the conductors ripped off, by the FD.

[areobat]

One thing that I find interesting - shocking really - is that from the pictures of the intact battery, there appears to be no attempt to provide a thermal barrier between the individual cells. This would seem to virtually guarantee that if ones goes, they all go - kind of like storing eight Roman candles right next to each other. If there was some sort of thermal barrier that could limit heat spread while the shorted cell uses up its energy and burns itself out, perhaps the other cells would remain intact thus greatly lessening the total damage. In the old days, a metal/asbestos laminate often worked quite nicely, but I'm sure more modern materials are available.

Another interesting observation is that there appears to be no direct cell temperature monitoring (to be fair, it may not be visible from the top). All I can see is what appear to be thermistors attached to each of the jumper busses. The thermal lag time from this arrangement would make it essentially useless for detecting cell thermal abnormalities (but at leas the totally non-flammable copper buss will never overheat!). Even my lowly Makita Li-ion drill has a thermistor directly attached to the cell casings.

[Machaca]

FlightPathOBN, Areobat, Lyman -- It appears the questions are coming full circle.

I suggest a re-read of the thread as several expert contributors have previously addressed these supposed new concerns.

[mm43]

@ Lyman,
I did not see the pin coupler, the battery was too fried. Again, though, re: the BC-1300 monitor/ is it dedicated to LITHIUM Ion?The BC-1300 series are for both Ni-Cad and Securaplane Lithium-Ion batteries.

The Battery charger BMS 50 pin connector J1 is connected to its complementary J1 connector on the Battery pack case. This should be obvious when viewing this exemplar pack (http://www.ntsb.gov/investigations/2013/boeing_787/photos/787_Battery_undamaged.jpg) courtesy NTSB.

P.S. The original link I posted of the front of the damaged JAL battery pack, was just that, the one under investigation by the NTSB.

[HazelNuts39]

I don't see any monitor wires going between the cells below their tops. Look at the RH picture (Cells on the right side) in RF4's link.

As to cell numbering, I think the sequence of cells connected in series is more logical, i.e. #5 at the rear and #8 nearest to the PCB's at the front of the battery case.

[mono]

Using temperature to shut down a battery (even with individual cell monitoring) will be closing the stable door after the battery has bolted! :ugh:

The lag between a short which could cause a runaway event and the associated temperature increase makes it an ineffective protection. what a short would do however is cause a significant change in the individual cell voltage/current characteristics. This, with effective algorithms to control it would be the most effective way to determine imminent runaway and take the battery off line.

As for monitoring. On a modern aircraft there are systems in place which will tell you the status of a contactor! Of course maintenance would have checked the CMC interrogated the BMS and it would, in association with the FIM, have pointed to the components to replace.

[green granite]

Using temperature to shut down a battery (even with individual cell monitoring) will be closing the stable door after the battery has bolted!

That would depend what is causing the temperature rise, if it is just due to the start of overcharging then the sensor would shut down the charger before any damage is done. If it's due to a short in the battery cell I agree with you.

[cockney steve]

re- the 50-pin data connector....don't get carried away by this, they're standard stock items, and the incremental sizes may well mean that , for example, you have 31 wires but the connector increments are 30-pin or 50-pin (would give you 19 "spare" pins)

Were the individual sub-cells to beindividually controlled(even if only with a fusible-link) the battery would still be able to perform it's primary function-emergency power-albeit at slightly reduced capacity....isolating a whole cell , not only reduces the capacity,but the output voltage....not good!

As designed at present, that doesn't appear to be an option as the inter-cell straps are bolted directly to the cell-terminal with no alternative switching to bypass a faulty cell.

I stand by my opinions expressed before, re-design/interface/quality. of all but the GS-Yuasa products which I believe to be beyond reproach.

[Lyman]

HazelNuts39

Yes, there are wires in the space between cell #2 and cell#3. Also, it appears some space for separation was allotted for isolation, at least between the above two cells. The Heat Damage seems worst at areas near metallic components. The case survived; had it been bigger, would there have been less damage to the nearby components?

Your numbering scheme is appropriate, but NTSB still got the "sides" wrong. The front of the Battery should determine the relative orientation, imo.

Question? Why such relatively massive connector bars? Why such close proximity to the Stainless Case?

Why is the Battery case placed so near the deck? Why not a stand off base, to prevent the kind of heat damage to the floor we see in the NTSB photo of the technician in the E/E bay?

I think the elements of compliant design are all there, but the dimensions, volumes are cut too thin.... There was ample room to accomodate a stand off base and more room between Stainless case and cells.... Not to mention the proximity to the bulkhead that supports the power panels.

Hind sight, eh?

[RR_NDB]

Hi,

HazelNuts39

A possible location for one or more temperature sensors... (http://www.pprune.org/tech-log/505695-787-batteries-chargers-33.html#post7689667)

I don´t believe the designers put independent temp sensors (8)

The connector, (well observed :ok:) seems confirm it (with fewer wires).

Apparently they just relied on the "patented algorithms" :}

Another possible reason to not use CELL SEPARATION. A BIG ERROR!

it´s clear to me the designers (including Boeing) were overconfident in the State of the art cells. (no heat, low internal resistance, long MTBF, etc.) :{

http://i.imgur.com/2iLmApE.jpg?1

[RR_NDB]

Hi,

mm43 @ # 635

patented charging algorithms

it seems, cell voltage history (JAL and ANA) were lost

PCB´s certainly are FUBAR and only option is what NTSB is doing now. By lack of other options (the "smoking guns" were certainly partially destroyed)

IMO Boeing obviously could innovate but:

1) The batteries replacement (VERY LOW MTTR) should prompt engineering attention.

2) Tracking on batteries performance (low performance) should started months ago. (could be just software inside charger)

Boeing high rocks were indeed concerned with what engineers said? :sad: :E

[RR_NDB]

Hi,

Bear,

Didn't ANA report a drop to zero voltage concurrent with the smoke event? (http://www.pprune.org/tech-log/505695-787-batteries-chargers-32.html#post7689161)

Yes, battery voltage went to ZERO because mother nature opened the circuit of the BAD DESIGNED BATTERY as i showed in the equivalent circuit of the probable sequence in an earlier post.

:E

[RR_NDB]

Hi,

mm43,

Charger faults - Fan speed, CPU Temperature, Voltage, Current, Power, Stored fault history.
Battery faults - Abnormal temperature, Temperature sensor circuit, Cell unbalance sensor unit.
LED display - Eight-character alpha-numeric.
Diagnostics - Self test, Output voltage, Output current, Operating hours, Temperatures, Power.
Time - Date, Software revision.
Charge mode - Bulk charge mode, Topping charge mode, Trickle charge mode. (http://www.pprune.org/tech-log/505695-787-batteries-chargers-32.html#post7689296)

1) Per cell temp. seems was not considered necessary

2) As we can see Software is now playing a role in batteries. :} There are THREE algorithms capable to stress this BAD BATTERY. Both JAL and ANA incidents could be related to this fact (use of patented algorithms)

But, how to verify? This can make impossible for NTSB answer (conclusively) WHY, the current effort.

As i mentioned before, we would need EACH CELL VOLTAGE HISTORY. The comments from JTSB and from IIRC NTSB on 32 V is ABSOLUTELY IRRELEVANT. Were certainly based in a quick look to FDR.

Questions:

1) Battery voltage (BEFORE relay contactor) is showed to crew? Is recorded in FDR?
2) Battery voltage (BEFORE diode module) is recorded?

IMO FDR config. for 787 should be a little bit different.

[Speed of Sound]

there appears to be no attempt to provide a thermal barrier between the individual cells. This would seem to virtually guarantee that if ones goes, they all go - kind of like storing eight Roman candles right next to each other.

No? :confused:

http://i1280.photobucket.com/albums/a481/SoS57/Ybat787c_zpsf9af567d.jpg

4-6 layers of steel and an air gap looks like a thermal barrier to me!

I'm not saying that it is necessarily enough, but there is clearly an attempt to separate the cells.

[Lyman]

Bear,

Didn't ANA report a drop to zero voltage concurrent with the smoke event?

Yes, battery voltage went to ZERO because mother nature opened the circuit of the BAD DESIGNED BATTERY as i showed in the equivalent circuit of the probable sequence in an earlier post.

Mother Nature? I don't think so. Give BOEING some credit. Temperature is obviously addressed in the design, to what extent is not known, but HazelNuts39 has shown some interesting leads in the failed case.

Just because they got caught out in their assumptions about propagation, does not infer that they let a high temp fail safe system out of the design.

I'm still looking at the "WhiteWad"....mesmerized.

[RR_NDB]

Hi,

Machaca @ # 655

I suggest a re-read of the thread as several expert contributors have previously addressed these supposed new concerns.

We can understand most of the reasons why posters are faster to post than to diligently read previous posts. This simply happens. It´s easier and immediate. :)

I would like to emphasize additional benefits in looking previous post:

1) We can learn from different views. Plural and rich.

2) Comments will be much more complete. Will take into account everything.

Worth the effort.

I remember i made this error in one of AF 447 thread on commenting something on "Remote FDR", before F-GZCP wreck was located. Anxiety explains. :)

[syseng68k]

RR_NDB:

Agreed and comes back to what I was saying about inadequate logging in
terms of the number of parameters stored. At a minimum, each cell's voltage,
cell temperature and charge / load current need to be logged to have enough
audit trail to trace back fault conditions to source.

From the info we have, it looks like the charger's led display provides the
equivalent of car's dashboard "idiot lights", which won't necessarily be
that helpfull to investigators.

FX: Message from Charger, "battery has failed". Fireman: Yes, thanks for that,
we just finished putting the fire out :sad:

I can see why they might only log a subset of the data, since logging all
at say once per second would take quite a bit of flash memory, but there
are ways round that:

Classify messages as to severity level: Informational, Warning and Critical

1) Informational messages re-use storage, deleting the least recent entries

2) Warning messages are saved until manually cleared, or out of storage,
then as per 1) above.

3) Critical switches to real time (1 entry per second ?) logging and saves all
parameters related to the fault.

The above is standard technique all over industry, so why not this charger ?...

[RR_NDB]

Hi,

SoS:

...but there is clearly an attempt to separate the cells.

A failed attempt that ultimately grounded a Dream...:mad:

The short circuit of cell # 3 (ANA TAK) was directly related of (improper) SEPARATION of the cells to battery case. I posted the equivalent circuit of this short that ultimately destroyed (fused) the ground green wire connecting the battery case to system ground.

Bear:

Mother Nature? I don't think so.

The short circuit was immediate! ("light speed" :} :) The temp monitoring was useless since then...:{

Mother nature action was INSTANTANEOUS. Certainly more than 1,000 Amperes from the cell # 3 plus terminal to ground. (A mili ohms load to the 12 Volts of Yuasa LVP 65 three cells)

[RR_NDB]

Hi,

syseng68k 2 # 669

From the info we have, it looks like the charger's led display provides the
equivalent of car's dashboard "idiot lights", which won't be necessarily be
that helpfull to investigators.

FX: Message from Charger, "battery has failed". Fireman: Yes, thanks for that,
we just finished putting the fire out

:mad: :)

The above is standard technique all over industry, so why not this charger ?...


This question will be answered by a serious govt. investigation or by a Richard Feynman style work (http://en.wikipedia.org/wiki/Richard_Feynman#Challenger_disaster) made after Rogers commission (http://en.wikipedia.org/wiki/Rogers_Commission_Report) Challenger SRB failure (also temperature related :} )

Feynman's account reveals a disconnect between NASA's engineers and executives that was far more striking than he expected. His interviews of NASA's high-ranking managers revealed startling misunderstandings of elementary concepts. For instance, NASA managers claimed that there was a 1 in 100,000 chance of a catastrophic failure aboard the shuttle, but Feynman discovered that NASA's own engineers estimated the chance of a catastrophe at closer to 1 in 100 (http://en.wikipedia.org/wiki/Richard_Feynman#Challenger_disaster)

:{

The commission members were Chairman William P. Rogers, Vice Chairman Neil Armstrong, David Acheson, Eugene Covert, Richard Feynman, Robert Hotz, Donald Kutyna, Sally Ride, Robert Rummel, Joseph Sutter, Arthur Walker, Albert Wheelon, and Chuck Yeager. (http://www.gpoaccess.gov/challenger/62_885.pdf)

[RR_NDB]

Hi,

mono:

The lag between a short which could cause a runaway event and the associated temperature increase makes it an ineffective protection. (http://www.pprune.org/tech-log/505695-787-batteries-chargers-33.html#post7690186)

Same problem when we put put finger in the soldering iron. When we feel it, too late. :}

[HazelNuts39]

The connector {well observed)Actually, Machaca spotted it in post #221. Credit where credit is due ...

[RR_NDB]

Hi,

mm43:

My guess is that THALES is the prime contractor and Securaplane is the sub-contractor providing the charger and BMS. (http://www.pprune.org/tech-log/505695-787-batteries-chargers-33.html#post7689837)

The smoking gun was two batteries labeled Thales. The label in the charger shows Thales responsibility is also in the "surrounding electric environment"

:mad:

[RR_NDB]

Hi,

HazelNuts39,

Machaca posted:

The lower harness (narrower connector on lower left) likely runs to a temp sensor under each cell. (http://www.pprune.org/tech-log/505695-787-batteries-chargers-12.html#post7659904)

Unless there is a similar connector in other PCB point i don´t think the wires are coming from temp. probes for each 8 cells. This (ideally) would require more wires. I would require 16 wires or a minimum of 9. The connector mentioned in Machaca post 221 and showed in the picture of your post may be for fewer temp sensor(s).

[areobat]

SoS -

There is a physical barrier between cells 2 & 3 and cells 6 & 7, however, only a small air gap separates cells 1 & 2, cells 3 & 4, cells 5 & 6, and cells 7 & 8. I guess that could limit damage to just half of the battery, but I suspect that four burning cells on one side of the physical barrier will easily supply enough energy to ignite the four on the other side of the barrier. In fact, I think Boeing has proven it - twice even.

[HazelNuts39]

The connector ... may be for fewer temp sensor(s)Perhaps three sensors, for redundancy and voting, just like there are three wires for each voltage.

[RR_NDB]

Hi,

HazelNuts39:

...just like there are three wires for each voltage.

Yes, may be. The designers (of the battery) clearly assumed temperature of the cells would not be a problem. "Brief" APU use, MAIN batt. use only in emergencies (remember for the first time in an airliner MAIN battery was put COMPLETELY out of the bus) and light use on ground (not so frequent use when not AC present, and towing)

So, the "patented algorithms" comes always to my mind. :E . i remember many years ago when working and living in a Skydive area i opened a li ion batt of a friend cameramen and found inside: Surprise! Electronics! I was shocked! All my k.I.S.S. principles came to my mind. :mad:

During all this days since Jan 7 i am designing a SAFEST (commercially speaking viable solution) and my charger WILL NOT USE ANY SOFTWARE for the critical cell charging. Just hardware (OBVIOUSLY REDUNDANT AND PROTECTED)

IMO algorithms should be made for help: Safety, etc. When relying on it for critical tasks you must have all means to FIRE them IMMEDIATELY when necessary.

The use of algorithms to optimize a DANGEROUS battery with ANY MECHANICAL PROTECTION against positive feedbacks (the so called here, thermal runaway) is : :mad:

I would like to analyze at least the schematic diagram of the harness on top of the cells in order to imagine what my colleagues had in their mind. Very probably they put redundancy on "balancing and sensing" wiring.

Certainly thermal aspects were not adequately managed. Temperature measurements, even in three different locations would not help too much. As it seems could be the case. Remember that:

In BOS AND ALSO in TAK the batteries were not supplying energy. (only if something like a diode module (TAK) or short circuit (BOS) but this possibilities seem were discarded by JTSB and NTSB.

Even a relay/contactor failure would not be sufficient for TAK case.

On redundancy i can sadly comment: We are observing redundant errors.

And the problems seems to come from "higher hierarchies" than just engineering/technical level.

[FlightPathOBN]

ICAO is moving to remove the exemption that allowed Li batteries on aircraft as cargo...

"A U.N. agency that sets global aviation safety standards is moving to prevent aircraft batteries like the one that caught fire on a Boeing 787 last month from being shipped as cargo on passenger planes, people familiar with the effort said.

Over the past few days, the members of the International Civil Aviation Organization's dangerous goods committee have proposed revoking an exemption that permitted lithium ion aircraft batteries as heavy as 77 pounds to be shipped on passenger planes, the sources told The Associated Press. All other lithium ion battery shipments on passenger planes are limited to 11 pounds or less because of the batteries' susceptibility to short-circuit and ignite."

[RR_NDB]

Hi,

A simple analysis (equivalent circuit) reveal ANA at TAK case was benign because battery (very probably) destructed an aircraft cable and was (due heat in cell # 3 plus terminal region) destroyed internally (opening) preventing it to continue the thermal runaway like happened in BOS. (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-40.html#post7691344)

The (probable) short circuit was: (http://www.pprune.org/rumours-news/505455-faa-grounds-787s-40.html#post7691355)

http://i45.tinypic.com/2nlqq79.png

Battery was bound to caught fire (like in BOS) but:

1) A short to ground created generated a thousand Amps current to ground from cell # 3 plus terminal, region.

2) This huge current "opened" the circuit.

PS

There is one point in TAK different from BOS:

JAL APU battery probably was at maximum charge level or approaching it.

ANA MAIN battery certainly lost energy during the short circuit.

Question:

This could explain why a fire (external) didn´t happen in TAK? Lower charge after intense discharge?

[Smilin_Ed]

All my K.I.S.S. principles came to my mind.

Thank you RR for bringing this up.

This whole situation is a massive violation of KISS. This technology, which to the most casual observer should have been seen as too immature, is simply not appropriate for this application.

In a previous life, my job was to look at equipment my employer was considering buying. I certainly would have asked a lot of questions about this Rube Goldberg lash up. Didn't the airlines' technical departments ever look at it or did they just buy "a pig in a poke?"

Obviously the designers realized the fragility of the technology and introduced a convoluted monitoring system (which really didn't work) instead of just using a mature technology which might have weighed a couple of hundred pounds more and been a hell of a lot safer. The cost saving realized by shaving a minor amount of weight from the airplane has already been wiped out in the last month of groundings.

It's fine and dandy to discuss what went wrong with the current technology but that won't get the planes back in the air. Boeing et al need to get to work and substitute a mature technology for this convoluted mess and get back to flying airplanes. :ugh:

[RR_NDB]

Hi,

FlightPathOBN:

All other lithium ion battery shipments on passenger planes are limited to 11 pounds or less because of the batteries' susceptibility to short-circuit and ignite.

Even 11 pounds as cargo in PAX planes could be risky.

:{

[RR_NDB]

Hi,

Smilin_Ed:

The cost saving realized by shaving a minor amount of weight from the airplane has already been wiped out in the last month of groundings.

:sad:

Boeing et al need to get to work and substitute a mature technology for this convoluted mess and get back to flying airplanes.


And it was just a battery...

:{

[FlightPathOBN]

I am wondering, and perhaps this has been addressed in this thread (somewhere)

But the white wires to the circuit board do not appear to have any heat protection, and it doesnt appear it would take to much to melt this bundle...what effect does one or a few of these wires have if shorted or disconnected?

[USMCProbe]

A friend of mine is a drag racer. His drag racing "hero" has a quote that he always repeats. "The best way to cut 100 lbs off a race car, is to find 1600 ways to cut 1 ounce."

There are thousands of ways Boeing cut a little here and there to achieve weight savings. Every aircraft designer before now, has made the same choices. If you don't think that way, you should design ships instead. Or maybe try being an architect. But not an aeronautical engineer.

It would be easiest thing in the world to add weight here or there to be conservative. But you cannot do that and succeed. To succeed, you have to find a way to do it lighter, and INCREASE reliability at the same time.

If the 787 did not have a few problems, I would lose respect for Boeings' engineers as not being professional enough.

[Lyman]

Light. Strong. Cheap.

Pick Two.

[Smilin_Ed]

There are thousands of ways Boeing cut a little here and there to achieve weight savings.

And in this case they compromised safety and DECREASED reliability.

[FlightPathOBN]

The battery system is just like all of the other pieces of this aircraft that were designed to the micron, without any regard to constructability and general realistic materiels tolerances.

Remember the delamination due to the carbon fiber shims being "out of tolerance" to design specs, by microns? :mad:

it is also interesting to note that Boeing designs and tests the components individually, such as a single wing assembly, while Airbus tests entire wing/fuselage assembly, not only in design, but in aerodynamic modelling and destructive testing...

[inetdog]

FlightPathOBN:
The battery system is just like all of the other pieces of this aircraft that were designed to the micron, without any regard to constructability and general realistic materiels tolerances.



A discussion in another forum accidentally led me to the following site:
Battery Life and How To Improve It (http://www.mpoweruk.com/life.htm)
Among other things, it explains that in addition to the lower chance of thermal runaway in an LiFePO4 cell compared to an LiCoO2 cell, the LiFePo4 has an almost zero volume change during charge/discharge cycling compared to as much as 11% in the LiCoO2 cell (Boeing 787), and that this repeated mechanical stress can damage the separator [leading to a short circuit]!
The fact that the Boeing batteries were unexpectedly being regularly discharged to a lower SOC than planned (because of ground operations error?) may be a critical factor in the reduced cell life.

[Lyman]

Hiya Hangtown....

When Hersman said that NTSB were going to look at the process of certification, and that included manufacture and suitability, she didn't have to elaborate.

BOEING might have missed thermal cycling, and wrinkling, pinching, and abrasion issues, plus pressure cycle as well.

Likely not. Which would be worse, they missed all that, or that they did not?

And fit that LiCoO2 anyway? And folded the electrode instead of winding it?

Welcome, nice to have someone here from El Dorado County....

This is a good read also:

http://www.nfpa.org/assets/files/pdf/research/rflithiumionbatterieshazard.pdf

:ok:

[ITman]

Thanks for sharing excellent document.

[Ian W]

@inetdog
The fact that the Boeing batteries were unexpectedly being regularly discharged to a lower SOC than planned (because of ground operations error?) may be a critical factor in the reduced cell life. Perhaps if an airline followed the rules/procedures for battery handling 'to the letter' repeated discharging to a lower SOC was inevitable? (In some areas this method of working is called 'working to rule'). I have lost count of the number of times when 'testing' a set of instructions that the author has said -"but nobody would do that!"

[Lyman]

Ian W

Thanks. That takes us back to the beginning, in a good way. There was an energetic discussion regarding the potential problem that resulted in the grounding. My first reaction, and others, too, was that it likely was an ops thing.

New Technology? Well, Yes. If a system is recognized as a challenge, it is incumbent upon the airframer to support its entry into the operational. Training, monitoring, on site assessments, etc.

Especially so if this innovative solution is flight critical?

ROLLS made a minor mistake in the design of its TRENT 900. It was recognized, AD'ed and rectified. But for a "Duff Oil Pipe", the mistake would have gone unnoticed, save by wonks who read the AD's.

The engine builder was in process with a suitable upgrade when QF had an uncontained event, far more serious than what we see with the 787, imo.

What can happen, WILL happen, unless one has a lucky bunny foot.

Were the FRP batteries an upgrade? Or Boeing's willingness to support a poor system with endless replacements at a cost of a quarter million a year per a/c?

I think BOEING had it figured out, was in process, and got caught out by the few units it was gettng to, but did not quite get the problem rectified.

Is there another way to see it?

:ok:

[syseng68k]

Ian W

For a critical subsystem like this, it would be better to have automatic disconnect of
the battery at min voltage level, rather than depend on someone remembering to
switch the lights off.

Such failures can be designed out...

[Ian W]

True, but perhaps it was not considered that someone would wait until that auto-disconnect or the level just before it - every single turnaround -

It might be instructive to look at the fleet of 787s that have been operating and see if every operator had the same battery turnover. Then compare the SOPs (and actual actions) of the highest and lowest turnover operators' .

[Lyman]

Ian W


Absolutely. The answer to the entire discussion is in those 150 Batteries, and the reasoning behind the accelerated replacement. Thus far, it is annoying to see NTSB Stalled on the two batteries TAK/BOS....


Those two are the effects. The CAUSE is in researching the FRP.

imo.

:ok:

[FASRP]

> There are thousands of ways Boeing cut a little here and there to achieve weight savings. Every aircraft designer before now, has made the same choices. If you don't think that way, you should design ships instead

Good ships are pretty sensitive to weight, especially where it is located. The new American LCS warships are deliberately not painted topsides to reduce weight. A decision they might be starting to regret ... we'll see.

[FullWings]

Looking at the pictures of the (fresh) 787 battery unit, the wiring layout and execution doesn't appear to be to the standard you might expect of a safety-critical device. Also, there seems to be just one solitary thermocouple in the middle under a gob of resin.

Contrast that with this (http://www.lange-aviation.com/htm/english/products/antares_20e/battery_system.html), the battery pack for a self-launching glider. Each cell is individually (and redundantly) monitored for voltage and temperature, with the facility to automatically heat the batteries to keep them in the ideal operating range if the OAT is low.

This isn't ultra-new technology, I think the above aeroplane has been around for at least a decade...

[Speed of Sound]

This is the 'shadow' of the connection underneath the 'white gob' in the centre of the battery.

Looks like the fixing lug of a thermocouple. :-)

http://i1280.photobucket.com/albums/a481/SoS57/787SENSOR_zps1396355b.jpg

[rogerg]

Just a question. Now that AB seems to be going back to ni-cad due to the uncertanty of lithium has the use of ni-nmh been considered. In model use they do the similar job to ni-cd but are lighter and smaller and seem to be pretty safe.

[Lyman]

All the talk about sensing temperatures at each battery, and even separate locations within each battery's cells, is a red herring. There is no way to "shut down" any one of the eight batteries connected in series.

One battery goes bad, the system shuts down. So why any more than one thermocouple?

The problem has always been propagation of thermal runaway.

When each battery of the eight battery group is short on life cycle, the entire group is short on life cycle.

This is all about compliance. The Backup 'system' flies in the face of even a one in ten million, the accelerated replacement program (ARP) is testimony to that.

Back to the regulations......

SoS... That "Thermocouple" is attached at......Battery #6? Almost as if it was planned that way?

:ok:

[Speed of Sound]

Now that AB seems to be going back to ni-cad due to the uncertanty of lithium has the use of ni-nmh been considered.

I'm sure it has but Ni-Cad is what is used on the 380 so as a late 'fix', it is better to go with something that should be fairly straightforward to certificate.

[RR_NDB]

Hi,

rogerg:


Just a question. Now that AB seems to be going back to ni-cad due to the uncertanty of lithium has the use of ni-nmh been considered. In model use they do the similar job to ni-cd but are lighter and smaller and seem to be pretty safe. (http://www.pprune.org/tech-log/505695-787-batteries-chargers-35.html#post7696608)

The strategy of EADS seems very good. Aviation uses Ni Cad (successfully)
Probably Ni mh was not NOW considered for the IMO GOOD move from EADS. Certainly was studied prior decision to use Li ion.

AFAIK Ni Mh is not being used in airliners. In the mean time (A350) could still adopt Li ion. If possible.

I think may happen in the future. A battery redesign is not so complex.

A BAD design "burned" the name Li ion. It has merits.

[syseng68k]

FullWings

Contrast that with this, the battery pack for a self-launching glider.
Each cell is individually (and redundantly) monitored for voltage and
temperature, with the facility to automatically heat the batteries to
keep them in the ideal operating range if the OAT is low.
Amazing and looks like a beautifully engineered piece of kit. Shows how
it can be done / should be done and wonder how the 787 managed to get it
so badly wrong.

Even if that wiring harness on top of the cells uses high temperature
cable, it would have been far safer to have physical separation. Perhaps
an overall moulding plate covering the cells, with small access holes for
each of the wires to screw down to the terminals.

As for the thermocouple, the group here have already discussed the
merits of individual temp sensing, but even cheap computer power supply
temp sensors do a more workmanlike job than that and are never just glued
on.

What were these people thinking ?...

[Speed of Sound]

and are never just glued
on.

To be fair, if it was glued on there wouldn't be a drilled mounting hole for it. ;)

[Lyman]

In the photo of the damaged batteries, the "Gob of Resin" is plainly visible, intact.

Could the 'drilled' mounting hole have contained a frangible plug, to secure the thermocouple, without conducting heat to it?

[Speed of Sound]

It looks to me like the thermocouple was mounted directly onto the inter cell shunt probably using something like this.

http://i1280.photobucket.com/albums/a481/SoS57/atsen_zps446ee5ee.jpg

As I said earlier in the thread, this single sensor was more than likely just a way of monitoring the ambient temperature inside the battery casing rather than anything more subtle.

[Lyman]

Hi SoS....

The resin gobbed "thermocouple". If a source of temperature sensing, could it be it is the sole sensor?

Would its placement more or less in the middle of the upper area be an attempt at a "generalized" reading?

It seems that no one battery can be "switched out" from the series?

The conjecture would depend on the design consideration. 170 degrees is the threshold of exothermic reaction at the Cathode, per the paper I linked. The Anode can go exothermic at lower temps, again the same paper.

Or could the "Thermocouple" be a fusible link of some description, tripping the main Battery breakers, in anticipation of runaway?

Is your photo of the "shadow" from the incident battery? Being empty, one wonders if the attachment itself might be the source of an open circuit, that trips the breakers? By design?

thanks for the photo :ok:

[Speed of Sound]

Yes, the 'shadow' picture is from the incident battery.

The thermocouple I pictured is purely a generic device whose mounting tab looks like something that could have been bolted to that cell linking strap.

I really don't think this sensor had anything whatsoever to do with cell monitoring or even thermal runaway. I think it is purely something to record the ambient temperature of the battery to see that it is remaining within the -X to +Y degrees specified by Yuasa. :cool:

[syseng68k]

SOS:

To be fair, if it was glued on there wouldn't be a drilled mounting hole for it.
Agreed, just the idea of a casual blob of silicon rubber anywhere inside that battery does
look like a bodge...

Anyway, looks like it will be grounded for months at least, with Boeing apparently
talking about strengthened titanium boxes to contain any fires :}...

[RR_NDB]

Dreamliner's assault and battery on Boeing's name (http://www.smh.com.au/opinion/dreamliners-assault-and-battery-on-boeings-name-20130129-2dj18.html)

:ok: This article confirm our concerns

Boeing readies short-term battery fix, facing uncertainty (http://seattletimes.com/html/businesstechnology/2020373450_boeing787xml.html)

:confused:

Boeing will not disclose any details of the solutions it is working on.

Let´s exercise:

1) A conventional bus with Ni Cd (MAIN similar to 777) and redesigned Li ion as stand by. (maintaining diode module approach)

2) Smaller Ni cd (APU) with redesigned Li ion as stand by.

Note: Ni cd´s in current Li ion locations and redesigned Li ion´s in special compartments in close vicinity (nearby FWD and AFT EEbays).

[inetdog]

From the second link, an apparent confirmation of speculation here about the temperature monitoring:
The battery control system will have sensors to monitor the temperature and voltage of each individual cell rather than the battery as a whole, one source said.
(Although I find it hard to believe that the existing system did not in fact monitor individual cell voltages somewhere along the way.)

I do not think any EV or other high total-energy use tries to avoid monitoring individual cell temperatures or does not at least use temperatures more closely linked to cell temperatures than the Boeing design does.

Even if it would not allow effective corrective action, at least it could deliver early warning and perhaps reduce the contribution of external charging power to the spread of thermal runaway. If the system did not detect the short of a single cell and raise an appropriate warning, it may not have disabled the charging attempt either.

[Lyman]

From the first photo of the series connection of the eight single batteries, why speculate there was individual monitoring? What could be done? Only one thing, switch out the entire battery group, at least to prevent any aggravation from continued discharge/charge?

All the talk about sensing temperatures at each battery, and even separate locations within each battery's cells, is a red herring. There is no way to "shut down" any one of the eight batteries connected in series.

It appears attempts to insulate each individual from another were made. Even if one could be switched out, that leaves the remaining number to be vulnerable to abnormal current and voltages? I think this system works as a unit, or it shuts down. NTSB states that JAL started with a single cell failure; designed containment failed. ANA the same?

An argument could be made that containment did function satisfactorily. That is a judgment FAA makes. But then it remains to also argue there was no "thermal runaway", only something 'less'. That might be a tough sell.

Trying to improve 'containment only' does not meet the regs. That implies a thermal runaway is tolerable. If it was, it won't be now....

NTSB would have to clear the current manufacture as something it has shown itself not to be, 'resistant to flame/fire'.

[Speed of Sound]

I'm sorry, but does anyone think there is a cat in hell's chance of the FAA certifying a stopgap where essentially the same arrangement is simply put in a bigger, more fireproof box?

Fair play to Boeing for perservering with Lithium Ion, but they need to face up to having to put the 787 on hold (alongside slowed production) for the best part of a year to do this. :-(

[Lyman]

Yes, I believe in such a cat. The paper is being written.

The Box? A heavier Gauge with hemmed top, to accommodate more and heavier fasteners. Which might be a mistake, the original puffed up, and deformed, but remained affixed. Separate partitions for each individual battery?

Will the box be elevated above the floor, on a stand off base? Will the box have a heavy duct, to transport gases out the hull? More Temp sensors, to facilitate an early shut off? Which of course defeats the purpose of the Battery?

What are the calculations for the box' ability to withstand explosive forces?

These are things that would have been folded into the development phase, had the design more accurately anticipated these failures.

The Accelerated Replacement Program? Boeing obviously knew the problem was the battery. If they thought the case was the issue, would they not have replaced the case along with?

This is a solution. It does not solve the problem of the Batteries. It solves the problem of the grounding.

[FlightPathOBN]

more from Boeing Land...

“The expectation in aviation is to never experience a fire on board an aircraft,” the NTSB chairwoman declared, her voice deliberate but dispassionate."


NTSB chief Hersman doesn&rsquo;t mince her words | In Person | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2020373620_hersmanprofilexml.html)

[RR_NDB]

Hi,

Reading some posts in the many threads created after 787 battery incidents it seems useful to remember, some important points on "Thermal runaway":

1) It´s a "positive feedback" mechanism. Once started (in a Li ion battery) it will make the device go to limits. E.g. leakage of electrolytes, generation of smoke and even fire outside the device.

2) A "positive feedback" to be interrupted (once started) would require to reduce the "device energy". In ANA TAK case this happened because battery was severely discharged by an "external short circuit". (caused by an internal short circuit of cell # 3 plus terminal region to ground through battery case). *

3) Electricity means (cut off, etc.) may be useless. It seems this is one characteristic of the BAD battery selected for the 787. This mean may be useless to stop battery charging or even delivering electricity (under load).

4) A simpler redesign of the battery would require reduce the likelihood of thermal runaway. This will be covered in another thread. (http://www.pprune.org/tech-log/508176-design-review-787-plan-b-a350-xwb-triggered-lithium-ion-batteries.html) For now a (technical) "quick fix" for 787 could be summarized:

a) Separate each LVP-65 ideally in individual chambers. (battery volume would be aprox. 30 ~ 40 % more)
b) Monitor each LVP-65 temperature (if not yet made)
c) Tweak software algorithms
d) Improve mitigation means. (better battery case, better venting, safer batteries location, etc.)

This is a Technical comment. Bureaucratic aspects (Cert., etc.) is another certainly much bigger issue for Boeing. :{

(*) This model can be explained by the ground wire that was fused by currents estimated in excess of 1,000 Amps. It´s a model, that could be confirmed or not.

[FlightPathOBN]

RR,

Make the batteries round like they are supposed to be! :ugh:

[Lyman]

Flight Path

“The expectation in aviation is to never experience a fire on board an aircraft,” the NTSB chairwoman declared, her voice deliberate but dispassionate."

A little clarity from a public official. She is doing a good job under difficult circumstances. Instead of learning from her example, The Director of the Department of Transportation, Ray LaHood, simply resigned. FAA spokesperson Huerta is likewise performing spin duty.

RR NDB

a) Separate each LVP-65 ideally in individual chambers. (battery volume would be aprox. 30 ~ 40 % more)

That is the current design. Each battery (erroneously called "cell") is contained in its own plastic box. Between these batteries, is a layered steel, insulate sandwich. A new design would be Steel pigeon holes, or "egg crate" enclosures.

Does nothing to prevent a thermal runaway. NTSB have concluded the JAL failure began with a single battery, #3. So any egg crate mod merely isolates the batteries from each other. Still possible is the prohibited "fire" to which Ms. Hersman refers.....

b) Monitor each LVP-65 temperature (if not yet made)

A noble attempt to.....what? Try to prevent fire? Once the temp is thresholded, the Batteries are shut down, the back up system is off line, and the purpose of the system competes with its "shutdown" feature".

c) Tweak software algorithms

To better "balance" charging? algorithms only peripherally "control" temps., and cannot mitigate exothermic reactions, the source of "runaway".

d) Improve mitigation means. (better battery case, better venting, safer batteries location, etc.)

All this does is underscore how badly Thales and BOEING designed the system in the first place.

If Director Hersman is accurate regarding her interpretation of "fire", the word "mitigation" is in direct contradiction. Fire is PREVENTED, not MITIGATED....

A new system for Aviation: "INFLIGHT FIRE MANAGEMENT SYSTEM"

IFMS.... really?

:ok:

edit. RR, just a suggestion re: the "short" at the connector strap. Look closely and see if you are not tempted to look at the deficit as "cut" by a gas jet, instead of a simple "fusion" due to heat of current. The battery case is aligned with the triangular "cut", and the metal has characteristics of a torch cut, complete with "beads" of molten metal along the very linear edges..... Is it completely severed?

[inetdog]

RR, just a suggestion re: the "short" at the connector strap. Look closely and see if you are not tempted to look at the deficit as "cut" by a gas jet, instead of a simple "fusion" due to heat of current. The battery case is aligned with the triangular "cut", and the metal has characteristics of a torch cut, complete with "beads" of molten metal along the very linear edges..... Is it completely severed?

Just a suggestion: Since there are so many pictures circulating whose captions even mistake which of the two batteries is shown, could you add a link to a picture of the area you are discussing?
If you are talking about the one I am thinking of, with the attachment nut sitting loose on top of the cell, a large part of the connector appears to be totally missing, not just cut. That is more consistent with a high amperage vaporization of the metal than with a gas jet cut, although both events may have occurred as slightly different times.

[RR_NDB]

Hi,

inetdog:

...a large part of the connector appears to be totally missing, not just cut. That is more consistent with a high amperage vaporization of the metal than with a gas jet cut...

What´s remarkable is:

Screw just disappeared. Section of strap too.

The model is:

Short to ground (a fact) discharged (fortunately) the battery (reducing thermal runaway risks and duration) and this high (1,000 Amps +) current opened the battery (Voltage recorded, after fluctuation, went to zero)

...although both events may have occurred as slightly different times.

Fact is: 5 Kg of the battery, gone. (electrolyte)

[RR_NDB]

Hi,

Bill,

That is the current design. (http://www.pprune.org/tech-log/505695-787-batteries-chargers-36.html#post7701865)

:=

Does nothing to prevent a thermal runaway.

:=

You will reduce drastically the likelihood of a DANGEROUS battery thermal runaway. BOS JAL was! ANA TAK, NOT!. A cell thermal runaway (with separated cells) is not a major problem.

A noble attempt to.....what?

To do a proper and safer battery management! When a given cell starts an internal short (BOS as per NTSB findings) it´s temp will be COMPLETELY different than the other cells. I seems (to be confirmed) the design of this BAD battery doesn´t process each cell temperature.

To better "balance" charging? := only:

The BAD battery algorithm will be reviewed, right? Let´s improve it. The opportunity is now to even derate the battery, if safety is the goal. And if this derating is not possible, SWITCH to Ni Cd´s as most of us would like. :mad:

It´s an ABSURD what´s happening. It´s just a battery. :mad:

All this does is underscore how badly Thales and BOEING designed the system in the first place.


Obviously this could help faster redesign approval.

"INFLIGHT FIRE MANAGEMENT SYSTEM"

Problem was FIRE. In TAK "mother nature" saved the day from fire: Due a HEAVY short circuit to ground. But 5 kg of sprayed electrolyte inside a EEbay is :mad::mad::mad:

[FullWings]

Back-of-a-fag-packet calculation:

Cell voltage 3.7V, capacity 65Ah, mass 2.75Kg, specific heat capacity 1,000J/KgK (guess)

(3.7 * 65 * 3600) / (1000 * 2.75) = 314K

The energy stored is enough to raise the internal temperature 300+degs in self-discharge before you take all the subsidiary exothermic reactions that go with thermal runaway. Looking at videos of disrupted lithium cells it is enough in some cases to take them to white heat and melt metal casings.

I can't see an obvious way to stop the heat bleeding through to other cells - the electrical bonding between them would carry significant flux even if the insulation of the walls was perfect.

As it stands at the moment, my personal opinion is that it is possible to have a safe installation of li-ion batteries in an airliner but Boeing have chosen the wrong chemistry together with inadequate safeguards. I agree with the NTSB that fire on board is something that just isn't acceptable, even if you think it could be contained. :ugh:

[RR_NDB]

Hi,

FullWings:

I can't see an obvious way to stop the heat bleeding through to other cells - the electrical bonding between them would carry significant flux even if the insulation of the walls was perfect.

Good point! :ok: Will think on this.

As it stands at the moment, my personal opinion is that it is possible to have a safe installation of li-ion batteries in an airliner but Boeing have chosen the wrong chemistry together with inadequate safeguards.

I agree.

I agree with the NTSB that fire on board is something that just isn't acceptable, even if you think it could be contained. :ugh:

Heat, smoke...but even fire! :mad: (and result: No backup energy)

Problem is. You need a dependable battery. That´s one (perhaps the more important) to switch now back to Ni cd. In the meantime a redesign would restore the confidence.

...even if you think it could be contained.

IMO, unacceptable. But if likelihood is lowered could be a short term "exit" to the stalemate.

I am studying the implications of a redesign to Ni Cd. (http://www.pprune.org/tech-log/508176-design-review-787-plan-b-a350-xwb-triggered-lithium-ion-batteries.html)

[FlightPathOBN]

re-design the batteries so they are round, take the reduction in cap, or make it a little bigger...the space between the cells could be filled with non-reactive material...(just like all the other LI systems out there!):{

the titanium shell cert would be 3 months....and it does not look like the FAA is even entertaining this...

to redesign the battery/charging/electrical system will take how long to design and then cert?

meanwhile, production rate is about what, 40 a month? at least 120 ac stored somewhere waiting for the temp fix...

for 6 months, 240 ac that would then have to be re-fitted, not to mention the ac already parked....

looks like Boeing should have let them go on strike, just to save the parking space...

[RR_NDB]

Hi,

FlightPathOBN:

to redesign the battery/charging/electrical system will take how long to design and then cert?


I am working on that and will post in the Redesign thread (http://www.pprune.org/tech-log/508176-design-review-787-plan-b-a350-xwb-triggered-lithium-ion-batteries.html)

meanwhile, production rate is about what, 40 a month? at least 120 ac stored somewhere waiting for the temp fix...for 6 months, 240 ac that would then have to be re-fitted, not to mention the ac already parked...


We can imagine the pressure from the suppliers for Boeing "keep the pace" :}

looks like Boeing should have let them go on strike, just to save the parking space...

:mad: :{ Complex situation

[Mac the Mechanic]

Home - Boeing 787 Updates (http://787updates.newairplane.com/Home)

Interesting link here.
Quote:- When the going gets tough, program teams get going:ugh:

[FlightPathOBN]

from that site...

"No battery-related incidents occurred before January 2013, when the airplane experienced two events."

Replacing over 100 of them so far is certainly an issue with the design and viability of the design.

[saptzae]

Progress in pinpointing Primary failure.

The plane's auxiliary power unit (APU) battery, which powers its systems when it is on the ground, was found to have swelling in two of its eight battery cells, the official said.Swelling found in second battery on All Nippon Dreamliner | Reuters (http://www.reuters.com/article/2013/02/19/us-boeing-dreamliner-japan-idUSBRE91I05920130219)

[green granite]

From the Boeing website referred to above, my bolding:

"Matching the right battery to the requirements

After extensive testing, Boeing ultimately selected the lithium-ion type battery because it has the right functionality and chemistry to deliver a large amount of power in a short period of time to do a high-energy task like start a jet engine. It then has the ability to recharge in a relatively short period of time so that it is available for the critical backup role that it plays during flight. Earlier commercial airplane models, such as the 777, 747 and MD-11, used nickel cadmium (NiCd) batteries, which are heavier, larger and less powerful.

Surely the bit I bolded there would preclude just stuffing it in a box to contain the fire?

[Lyman]

There can be no conflict in the regulations. ICAO has ruled no large Lithium Ion batteries on board aircraft.

The DOT (Department of Transportation) ruled, hastily, to allow these batteries in cargo, just as Boeing was hurriedly shipping them to replace batteries in the field. That raises a flag. After the grounding, and an initial statement of support for Boeing, the chief, Ray LaHood, resigned the position. Part of politics is anticipation. NTSB are investigating the certification of the 787. To get fire acceptable in there, somewhere, will take some interpretation.

What is the current status of this cargo/Battery?

There is argument that since the FAA do not specify fire as disqualifying in their regulations, that it is allowed, if contained.

To contain is to prevent from spreading.... It is the first step in fighting a fire. The second step is to extinguish the fire. As we see in Boston, extinguishing this type of fire is not generally possible.

What are the regulations per the transport of a box of non-extinguishable fire, aboard a flammable airplane? In non accessible areas of the airframe?

[Ex Cargo Clown]

I'd be very wary of using a Ti alloy, just another lightweight solution to a bigger problem. 400 Degrees plus and you are in big trouble.

[cockney steve]

Since entering service, Boeing 787 Lithium-Ion batteries, each with eight cells, have logged more than 2.2 million cell-hours on the ground and in the air during more than 50,000 flight-hours. No battery-related incidents occurred before January 2013, when the airplane experienced two events. Investigation into these events is in progress.

Above taken from the Boeing "damage-limitation" website.


Well! what a complete load of pseudo-engineering bollocks :yuk:
2.2 million "cell-hours" on the ground?-REALLY!(less 50,000 actual flight hours*) well, fxxk me with a fountain-pen, my Ford has had about 8 billion millilitres of Diesel through it's system, with NO "incidents"...keep changing the filter sees to that!:} (is that similar to "keep changing the batteries when they go T.U.?"

Where they find these smart-ass political -spinner oil-slick smarmy bull****ters from, I've no idea. As a potential Boeing Pax. I won't believe another word from them,if this is how they patronise their market.

So, let's do the sums...the "battery hours" are actually nearer 250,000(assuming that the quoted 50Khours was "battery time" and not "cell-time":} ) BUT WAIT!..each aircraft has 2 batteries....50 grounded,=100 batteries...add 150 changed-out....250 total used stock

so the cumulative service life of these aircraft, (land and ground,-their figures) is 250,000 hours that means a total service-life of 1,000 hours per battery OR 16 dollars an HOUR ....32 DOLLARS an HOUR, EVERY hour per aircraft....remind me, how much is a Laptop battery? price? hours life? Oh! I see, I got it wrong! the cost doesn't matter as long as it's a good, reliable ,fit-for purpose system. WOT? NONE of the above?:O

Some bean-counter's being grossly overpaid for a stupendous level of incompetence!

* also back-of-a-fag-packet calculations.

[TURIN]

After extensive testing, Boeing ultimately selected the lithium-ion type battery because it has the right functionality and chemistry to deliver a large amount of power in a short period of time to do a high-energy task like start a jet engine.

Eh?:confused:

The main bat has nothing to do with engine start.

A ni-cad will do the job of starting the APU.

Someone at Boeing got their wires crossed. :suspect:

[Hi_Tech]

I am joining late on this thread, but after reading through the 37 pages of posts. There appears to a lot of battery experts on this thread, discussing about temp sensors, cell separation etc.
But no body seems to discuss why
1. Boeing never experienced this problem during 3 years of flight tests and ANA during nearly an year of operation.
2. Is it just a coincidence that we have 2 fire incidents in one month.
3. Surely the battery would have gone through a rigorous testing before manufacture and it is difficult to imagine that there were no problems at all with this compact design of a highly volatile chemistry.
4. What was the reason for 100 batteries removed before these incidents. No alarms were raised for a new aircraft.
4. From the data available with me, these batteries perform almost the same function as on Boeing 777, except for emergency breaks from Main battery, in case of a total loss of power landing. Then why B787 require a battery that can give 150 amps?
Can some one with the required knowledge and info enlighten.
It is sad to see Boeing fortify this volatile battery with thicker walls just to get the airplanes airborne again. You only need another incident, even if contained fully, for the travelling public horrified even to go near the aircraft. Remember the well engineered DC10 that disappeared along with the company. Boeing's venture on a bleed-less road was risky enough, but this route is a very risky for them and the airlines. I hope FAA and NTSB will think twice before they give the green signal. :=

[ITman]

Having read both threads on this issue there is a lot of good information being provided. The swelling of the packs is quite normal if you draw the maximum permitted C rating of the pack. Having experience in LiPo packs has shown that if the discharge current is over 50% of the maximum C rating they will swell and get very hot. I am sure that these issues were considered in Mr B's design, at the same the start upn surge current from any motor whether AC or DC is considerably more than the constant current and this is not going to help these packs survive a sensible reliable life if it is greater than the rated pack C. The pack also loses its storage capacity over time if this continually done.

One hopes that Mr. B has done all the calculations and checks on the discharge of the battery packs.

[saptzae]

@Hi_Tech
All I can contribute wrt your questions is that more than 100 Batteries were replaced, whereby one may speculate that it was bound to happen.

The only hint of progress on Primary failures was today when anomalies were found by JTSB in ANA APU battery. (#729)

@ITman
My estimate for max charge current is 0.7C and for max discharge current 4C in case of APU battery and 2C in case of Main battery.

These LiCoO2 cells are de-rated to 4.025V, and should not show any anomalies after a few months / a few hundred flight hours.

Edit: Peak currents are a lesser concern these days as all heavy loads are inverter driven, and that with soft start, without which, an inverter driving a variable frequency load, such as a starter generator, would not survive.

[Lyman]

Here is the language from THE FEDERAL REGISTER....

. To address these concerns, these special conditions adopt the following requirements:
• Those sections of 14 CFR 25.1353 that are applicable to lithium ion batteries.
• The flammable fluid fire protection requirements of 14 CFR 25.863. In the past, this rule was not applied to batteries of transport category airplanes, since the electrolytes used in lead-acid and nickel-cadmium batteries are not flammable.

The electrolyte in the Battery is flammable, hence the applicable rule. So long as
The aircraft uses flammable electrolyte, it would seem the rule applies.

So, what is the requirement....?

Title 14: Aeronautics and Space

CHAPTER I: FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION

SUBCHAPTER C: AIRCRAFT

PART 25: AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

Subpart D: Design and Construction

: Fire Protection

25.863 - Flammable fluid fire protection.

(a) In each area where flammable fluids or vapors might escape by leakage of a fluid system, there must be means to minimize the probability of ignition of the fluids and vapors, and the resultant hazards if ignition does occur.

(b) Compliance with paragraph (a) of this section must be shown by analysis or tests, and the following factors must be considered:

(1) Possible sources and paths of fluid leakage, and means of detecting leakage.

(2) Flammability characteristics of fluids, including effects of any combustible or absorbing materials.

(3) Possible ignition sources, including electrical faults, overheating of equipment, and malfunctioning of protective devices.

(4) Means available for controlling or extinguishing a fire, such as stopping flow of fluids, shutting down equipment, fireproof containment, or use of extinguishing agents.

(5) Ability of airplane components that are critical to safety of flight to withstand fire and heat.

(c) If action by the flight crew is required to prevent or counteract a fluid fire (e.g., equipment shutdown or actuation of a fire extinguisher) quick acting means must be provided to alert the crew.

(d) Each area where flammable fluids or vapors might escape by leakage of a fluid system must be identified and defined.

[Amdt. 25-23, 35 FR 5676, Apr. 8, 1970, as amended by Amdt. 25-46, 43 FR 50597, Oct. 30, 1978]

[FlightPathOBN]

RR NDB,

Here is my suggestion, from a completely different engineering point of view....

In the re-design, go back from 32V to 24V..
the would allow the room for round cells, and some space between them, in the same box.
This would also negate the need for the stepdown transformers for the voltage....

[bubbers44]

The 787 uses starter generators for engine start, not pneumatic starters like other Boeings.

[saptzae]

@bubbers44
The 787 uses starter generators for engine start, not pneumatic starters like other Boeings.
Yes, twin 250KVA, and which are powered by twin APU 225KVA starter generators.

Only the APU is started from a battery, which IMHO will draw less than 7.5KW (300A x 25V).

[DType]

Aeroplanes have been living with fire (in their engines) for over 100 years. This COULD be a precedent for permitting (inadvertent) fires in another power source, the batteries, provided it was as well contained as the engine combustion???

[Kiskaloo]

FlightPathOBN:
meanwhile, production rate is about what, 40 a month? at least 120 ac stored somewhere waiting for the temp fix…

Current production is four frames at Everett and one at Charleston per month. The plan is/was to be at 10 per month across both FALs by End-Of-Year.

FlightPathOBN:
"No battery-related incidents occurred before January 2013, when the airplane experienced two events."

Replacing over 100 of them so far is certainly an issue with the design and viability of the design.

The 100 replacements were due to the battery shutting down due to being over-discharged. As over-discharging can induce thermal runway, the system is designed to shut the battery down when it reaches a specific level of charge. So in these cases, the battery safety systems were operating as designed.

[RR_NDB]

Hi,

Dtype:

Aeroplanes have been living with fire (in their engines) for over 100 years. This COULD be a precedent for permitting (inadvertent) fires in another power source, the batteries, provided it was as well contained as the engine combustion???
(http://www.pprune.org/tech-log/505695-787-batteries-chargers-38.html#post7703665)

You introduce an important point: We operate (and live with) machines with contained fires. What is not accepted is:

A company introduce a new design (under special "conditions") and in an interval of days two planes suffer incidents with HEAT, SMOKE and FIRE (BOS). The second (TAK) was bound to be much worse. A short circuit saved Boeing discharging the battery thus avoiding an in flight fire in a compartment with important electronics. (This is a model posted and commented earlier)

The technical answer is:

A dependable and safe battery (one that not is transformed suddenly in a dragon: heat, smoke and even fire) is absolutely required. A battery (that could caught fire) well contained with "normal" MTBF will be certified.

Problem now is not only technical. Became almost a "political" issue with not small technical challenges.

(*) No powered plane without fire. There are powered (http://www.eads.com/dms/eads/int/en/Our-Innovation/Technology-Licensing/Latest-news/ILA-Berlin-eGenius-story.jpg) planes (electric motor) with these batteries.

saptzae:

IMHO will draw less than 7.5KW (300A x 25V).

Good estimate

These LiCoO2 cells are de-rated to 4.025V, and should not show any anomalies after a few months / a few hundred flight hours.

What really happened? :confused: Just random? Coincidence?

FlightPathOBN:

In the re-design, go back from 32V to 24V..

32 V was designed due BDM (diode module)

ITman:

I am sure that these issues were considered in Mr B's design,...

We detected errors so, we are not so confident on that.

Hi_Tech

2. Is it just a coincidence that we have 2 fire incidents in one month.

One fire incident in BOS (Logan) TAK had heat, smoke and hot chemical spray (battery lost 5 Kg) :}

3. Surely the battery would have gone through a rigorous testing before manufacture and it is difficult to imagine that there were no problems at all with this compact design of a highly volatile chemistry.

We don´t know. This is a Testability issue.

TURIN:

Someone at Boeing got their wires crossed.:suspect:


The disconnection seems not just between engineers at Seattle and Chicago high rocks. :{ :mad:

cockney steve:

Some bean-counter's being grossly overpaid for a stupendous level of incompetence!

:mad:

green granite:

It then has the ability to recharge in a relatively short period of time so that it is available for the critical backup role that it plays during flight.

Logical question! :)

[EEngr]

cockney steve (http://www.pprune.org/members/211915-cockney-steve):

so the cumulative service life of these aircraft, (land and ground,-their figures) is 250,000 hours that means a total service-life of 1,000 hours per battery OR 16 dollars an HOUR ....32 DOLLARS an HOUR, EVERY hour per aircraft....If my airline starts putting a battery surcharge on my ticket, I'm blaming you for giving them the idea.;)

[Lyman]

Hi DType

I had thought of that, looked at the applicable rule, and see some room for something like what you say.

(a) In each area where flammable fluids or vapors might escape by leakage of a fluid system, there must be means to minimize the probability of ignition of the fluids and vapors, and the resultant hazards if ignition does occur.

Leakage of electrolyte is associated with expansion and heating of the battery case, causing a crack.

Leakage, in the rule, is not constrained, but addressed only in that it may ignite.
If the temperature of the interior of the battery and its enclosure can be kept below the fluid's ignition (flash) point, leakage, per se, is not prohibited.

That satisfies "minimize the probability of ignition." It does not say "Possibility", and minimizing a "probability" is less constraining (easier) to do. So in the case of the fluid and vapor leakage, "possible" leakage is allowed.

Now, "the resultant hazards if ignition does occur." That means the results of ignition must be "minimized". That does not mean "controlled", or even "mitigated". If the burning electrolyte is contained in the enclosure, that would satisfy the "minimize" part of the langauge.

BUT:
Electrolyte escaped from the Battery in the JAL accident, and it is assumed it continued to burn as it flowed along the EE Bay decking. This would likely NOT be allowed by the rule, so "containment" enters the controlling language.

(2) Flammability characteristics of fluids, including effects of any combustible or absorbing materials.

What if the electrolyte, alight, puddled in an area of CFRP? (Carbon Fiber Reinforced Plastic). This is potentially a show stopper.

CFRP ignites at 580 degrees Fahrenheit. By demonstration, CFRP must be proven not to ignite at the temperature of burning electrolyte. If it cannot, the CFRP is combustible, by rule, and leakage is prohibited. NEVER ALLOWED.

The fuselage is constructed of this material (CFRP). If it catches fire, it will burn on its own, in continuous fashion, until extinguished by an approved method. If it ignites in the Hold, extinguishment is not possible until landing. On board extinguishing is not provided, and would be in conflict with the rule making anyway, CFRP cannot ever be allowed to ignite, under any condition. What are the products of burning CFRP? If these combustion by-products entered the flight deck or cabin, is the air breathable?

Back to the drawing board. A box that cannot leak is required, by regulation. Any breach of the contents of the enclosure MUST be dumped overboard, if the contents are burning, the exterior of the Hull is at risk to ignite.

[inetdog]

Mac the MechanicHome - Boeing 787 Updates (http://787updates.newairplane.com/Home)

Interesting link here.
Quote:- When the going gets tough, program teams get going
Another interesting quote, which indicates to me that the site was put together in a big hurry without proofreading by someone with a technical background:
On the ground, the 787 can be started without any ground power: The APU battery starts the APU generators, which start the APU to power the engine generators, which then start the engines.
There an excusable confusion between a generator and a motor-generator or starter-generator, but the idea of starting rather than powering a device "which then...." implies that it is running before the associated APU or engine starts to turn over.
I also believe that only one of the two APU generators at a time is involved in the APU start.
Details may not matter in publicity, but they matter when discussing the engineering.

[FullWings]

Aeroplanes have been living with fire (in their engines) for over 100 years. This COULD be a precedent for permitting (inadvertent) fires in another power source, the batteries, provided it was as well contained as the engine combustion???
Aeroplanes have also been living with a means to cut off the fuel to a burning engine for over 100 years.

If the batteries in question were installed so that they could be isolated, then doused with large quantities of water (paddling pool volumes) and/or ejected from the airframe, then it might be worthy of consideration.

No pilot that I know would be happy with a piece of equipment in an inaccessible area that was a demonstrated fire risk, "contained" or not. What's the point of all the dangerous goods legislation if you carry something similar to a prohibited item around with you all the time?

[saptzae]

@RR_NDB
32 V was designed due BDM (diode module)32.2V is end of charge voltage (4.025 x 8).

29.7V is rated voltage.

I'd go for 25V being available when battery low and at a high current load.

I estimate that BDM drops less than 1V (0.8V typ) at 150A if based on Schottky diodes and less than 0.5V (0.3V typ) if based on MOSFets.

NiCad rated bus voltage is about 24V and end of charge 29V for 20 cells. End of charge less 27-28V at elevated temperature.

What really happened? http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/confused.gif Just random? Coincidence? My best bet, as outlined in earlier posts, Primary failure (short) due to gradual cell deterioration after one or more (in no particular order of preference) of :


Mismanagement by BMS.
Mishandling (assembly, rework, repair, maintenance, storage)
Mishandling deep discharge and reset BMU lockout
Mishandling external over voltage, such as bus over voltage, also during maintenance or storage (recharging - dunno they do that).
Tested to overstress - Boeing says they test a lot and hard (unlikely IMHO)
Bad cells (unlikely IMHO)

Edit: Apparently, current battery tests do not detect cell deterioration. I do not claim that tests possibly could detect it.

[bill good]

Redesign - remove all batteries & use super capacitors. End of story!!