787 Batteries and Chargers - Part 1

[RR_NDB]

Cause or symtom?

RetiredF4:

Hi Franzl,

Sequence in ANA, very probably:

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:

(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]

Thanks RR_NDB

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]

Complementing posts 497 and 498

Hi,

Probable major short circuit path



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.




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

[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.

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.....

[Rocchi]

Possible mechanical damage at assy.

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]

Thermal runaway

@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]

Question from a "non tech." person

On the spec. for the cell in the B787 battery, http://www.s399157097.onlinehome.us/...s/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?