787 Batteries and Chargers - Part 1

[inetdog]

SaturnV:
The NERVA engine, never operational, used only liquid hydrogen for fuel, but it was a nuclear reactor.

I know what you mean, but the NERVA used hydrogen for reaction mass only, not fuel. The lighter the molecules you throw backward the more thrust you get for the same power. It was not a fusion reactor. :8

[saptzae]

@rottenray

I second your post in its entirety.

Talking is just so much easier than understanding.

I read sites like pprune and avherald pretty much since their beginnings. Read, to learn. This is the first thread i contributed to. It is almost regrettable. The amount of noise is astounding and it seems to increase.

The industry has seen its share of design induced failures and learned from it. Some examples with fatal outcomes are: Comet square window fatigue failures, Electra whirl mode wing failures, 737 rudder pcu reversal.

In this case, no one got hurt. Plenty of red faces though, this is good. I once had an engineer fly in to find my design error in 5 minutes. I shall never forget.

Technology gets ever more complex. it takes time to learn and apply.

My background is electro mechanical engineering, I went into micros age 17, assembling code by hand. I do mostly systems software (C/C++/JS) these days.

I am amazed how far young developers are removed from "deep" understanding of systems.

Things get abstracted. A does A, B does B, C does C.... Interfaces A<>B B<>C are defined but nobody will understand all permutations of interactions of A, B, C, especially when something breaks.

As we read often here, young pilots face similar problems.

It takes a positive mindset and do the best and learn and try again.

Back to topic.

Boeing needs to get the planes back into the air.

Their proposal is better management of the cells, more insulation and an additional layer, the firebox. IMHO, it will be sufficient to address the issues at hand, and mitigates further failures.

In short, the approved solution will be safe by the letter of the law.

I may wish to do more, for example it seems that the charger charged the failing battery for 3-4 seconds. I would like to avoid that. Anyway, improvement is incremental, it never ends.

The entire industry will benefit from this incident, as it did from incidents in the past.

[inetdog]

RetiredF4:
http://www.boeing.com/787-media-resource/images/graphics/Infographic-787Battery-English.jpg
Looks like that link is dead at the moment. (Died of embarrassment?) I did see what I think was that image from an earlier published article though. The main change was in the descriptive callouts. And the fireproof top layer. Not sure if anything else changed in the image.
Maybe it was just intended to show where the changes would be made and not what they were.

[pax2908]

The new battery enclosure will still be pressurized?

[Kiskaloo]

@tonytales
I wonder how long the airlines will be able to stand what was already an apparently abnormally high battery replacement rate prior to the fire/overheats.

The cause of those replacements was predominately due to the battery being too deeply discharged by ground staff using it during operations like refueling and tripping safety systems.

Boeing is raising that limit so I guess that means when the battery cuts-off, it will be at a charge level that will allow the onboard charging system to bring it back up and it will no longer need to be removed.



Here is a YouTube Clip of part of the Boeing presentation on the changes they are making to the battery system - Boeing 787 Battery System Solution - YouTube

[cockney steve]

full marks to the commentator who got through the whole of his spiel without once sniggering. Me- i laughed aloud!

Of course, it's Youtube, therefore, it's designed to appeal to the masses of mushrooms out there.

Are the rest of you convinced?

Forgot, the overflow pipe is Titanium, so that's OK then (looks like domestic plumbing to me!)
Per my remark on the R&N thread....poke the pipe out of the tailcone and the burning, toxic crap will eject into the jetstream......Hell, that commentator could keep a straight face and pass it off as automatic thrust-jet augmentation to get the aircraft back to land quicker.

See! Mr. Boeing! I can bull**** with the rest of them....got a cushy overpaid job for me?:}

[Kiskaloo]

Hot, liquid electrolyte exited the forward EE bay of NH692 via the outflow valve and it did not damage the fuselage beyond leaving a brown streak on top of the white paint.

[Lyman]

The only closeup photo I saw of the forward scupper showed the aperture completely covered over with film, and tape.

[tonytales]

Kiskaloo
Thanks very much for you update and the Boeing video. I am persuaded that they have indeed produced a container sufficiently strong and heat resistant to hold the worst case failure. A steel plate box 0.250" thick does raise my eyebrows as to weight.

Speaking as a maintenance person of long experience, changing the battery has now gone from releasing a couple of hold-downs and a screw-on battery connector to removing and reinstalling a considerable number of fasteners around the periphery of the cover and maintaining a large seal as well. Will it require some pressure check after reinstalling?

I surely hope that the change in the on-board recharging spec by Boeing cuts down the number of battery changes required and that most of the previous changes were for that reason alone. The fact that the battery seemed to be easily depleted below that value used before by the simple use of it for ground servicing seems strange.

I salute Boeing's tenacity in trampling down the perceived problem and I hope the fixes put the whole thing to bed.

[PickyPerkins]

I have been reading parts of the FAA docket at:
Accident Investigations - NTSB - National Transportation Safety Board (http://www.ntsb.gov/investigations/dms.html).

Old stuff, but interesting.

The battery Boeing wanted.
Page 15 of the above docket refers to a Boeing Specification Document” (SCD) which is used to describe an individual airplane component.

The SCD referred to states that “The [APU] battery shall be capable of supplying 18kW constant power for 45 seconds to the Start Power Unit (SPU) with a minimum battery terminal voltage of 20V for three consecutive APU start attempts with 60 seconds rest between each start attempt”.

18kW at 32Vdc needs 562A, and at 20 Vdc needs 900A.

So Boeing was expecting the APU battery to supply between 562A and 900A for 45 seconds at a time.

In contrast,
The battery Yuasa supplied.
The 787 batteries are made up of several Yuasa LPV65 batteries in series. The same current passes through all the batteries.

These batteries are 75Ah types with a Yuasa specified maximum discharge rate of 5C, or 5x75 = 375A.

So Yuasa was not expecting to provide more than 375A.

How much current does an APU on a 787 actually take to start?
The FAA noted this disparity (562A or more called for by Boeing vs. 375A maximum available from the Yuasa batteries).

They then noted that the APU on the incident aircraft actually used less power than the Boeing SCD called for, and that there were sudden changes in power consumption during the start sequence, but that testing was done with “resistive banks”.

The FAA docket says that a start on the APU on the incident aircraft took 35 seconds and actually used power as follows:

Initially about 9.6kW (32V at 300A)
Then 8.7kW
Then 10kW for 10 seconds
Then 4kW
10.3kW for about 20 seconds
Then zero for 47 seconds
Then charging at 46A.

If the voltage available is 31V or less, then the maximum APU start power of 10.3kW requires at least 332A and probably more.


It would be interesting to know what factor limits the Yuasa battery current to 375A?
And is this limit independent of temperature, and of the duration of the current?

BTW, is there any information about how many of the 150 replaced batteries were APU batteries and how many were main batteries?

[inetdog]

PickyPerkins:If the voltage available is 31V or less, then the maximum APU start power of 10.3kW requires at least 332A and probably more.

This, at least for the APU start battery, indicates that some proposals here about using a battery design that would allow dropping a single failed cell out of the series string, thus allowing continued use of the battery if necessary, might not be feasible.

[cwatters]

So they propose adding insulators and tape and wrapping the whole thing in an outer steel box... Is there any additional cooling to compensate in hot climates or isn't that needed?

[syseng68k]

PickyPerkins, #1009:

That's an interesting post, thanks, though are there typos in the battery
load timeline ?:

Initially about 9.6kW (32V at 300A)
Then 8.7kW
Then 10kW for 10 seconds
Then 4kW
10.3kW for about 20 seconds
Then zero for 47 seconds
Then charging at 46A.
If you have an accurate timeline, then you can calculate the total
watts hours needed to start the apu. It's quite easy to have profiled
current limiting in the apu starter electronics, since it's inverter
driven and start time trades off against max starter current. The
20v minimum seems a bit iffy, in that each cell's voltage will be 2.5v,
at that point. So, what will the cell voltages be when a start has
completed from 20v ?. Less than a min safe voltage, or what ?. The final
point being that the cell data sheet only lists discharge characteristics
up to 250 amps, with nothing after that, yet they are driving these cells
at 300 amps ?. My take on it is that they skimped on the cell spec and
should have used cells of much higher ampere hour capacity for this
application. The weight saving obsession must have it's limits at some
point.

Aviation kit is usually designed to have a higher margin of safety than it's
commercial equivalent. I would have thought that they would at least have
doubled the cell capacity in relation to max expected load. To do this would
mean larger cells, but perhaps longer service life and less prone to
catastrophic failure. Running components well within ratings improves
reliability, all else being equal, but these batteries are being pushed hard.
High current to start the apu, then fast charging within short timescales,
both of which will cause significant temperature rise and perhaps hot spots
due to varying resistive paths within the cell.

Let's hope they get it right, but the proposed solution seems light on
detail in terms of what changes will be made to battery management and
charging. Afaics, there is still only a single current sensor. There's
no mention of improved temp sensing, non volatile logging for the cell
voltages, contactor fail safe or other items, though some of this was
hinted at online a couple of weeks ago.

As for the strengthened enclosure, reminds me of the old black joke about
fusing: If the fuse blows, put in thicker wire and if that also blows, put
in a paperclip :ugh:...

[PickyPerkins]

Syseng68k Post #1012

Total energy for APU starts does not seem to be the problem, because even the Boeing 18kW spec. only needs about 30% of the energy stored an a fully charged battery (though not all that energy is available energy).

Boeing requirement was 18kW x 45 seconds x 3 = 0.675 kWh
Battery stored energy is 75Ah x 32V = 2.4kWh.

Current is the problem.

I should have mentioned that the FAA docket said the APU took only 35 seconds to start, which is less than the 45 seconds in the Boeing SCD.

Just to be sure that I understand your post, are you suggesting that the inverter may have been limited to taking something like 375A max. and was able to start the APU in 35 seconds with this limitation? (I know nothing about APUs.)

[PickyPerkins]

If you have a partially full barrel of oil and keep it though several summer/winter temperature/humidity cycles you will usually find a layer of water at the bottom. During the summer humid air enters the air space above the oil and in the winter this moisture condenses and descends to the bottom of the barrel, where it remains trapped.

http://i1343.photobucket.com/albums/o796/gone4weat4pa2/bth_condensation_barrel_zps870f8fe9.jpg?t=1363541871

Now, bear with me, because there is a point to all this.

I have had a similar experience with a steel pipe with a plate welded to the bottom used to support a girder over my garage. Over a period of 30 years condensation within the pipe rusted the inside of the bottom of the pipe to the point where it fell over onto the floor!

http://i1343.photobucket.com/albums/o796/gone4weat4pa2/condensation_pipe_zpsf7a54d03.jpg

This accumulation of water may happen in any nearly sealed enclosure subject to temperature/humidity cycles where the condensate cannot drain away.

I was therefore very interested to see a detail of the new Boeing battery box, as follows, “Finally, a set of changes is being made to the battery case that contains the battery cells and the battery management unit. Small holes at the bottom will allow moisture to drain away from the battery and larger holes on the sides will allow a failed battery to vent with less impact to other parts of the battery.”
Boeing Provides Details on 787 Battery Improvements - Mar 14, 2013 (http://boeing.mediaroom.com/index.php?s=43&item=2622)

So maybe they think condensation had a role in the failures, and now there is to be no attempt to seal the battery box. Condensation will be allowed to drain out of the box. The stainless steel enclosure will be vented to the outside but otherwise sealed, and I suppose that enclosure will accumulate water just like my barrel of oil unless some provision is made for a drain. But at least the condensate will be in the enclosure and not in the battery box.

The Boston event occurred on Jan. 7, and I seem recall that the aircraft arrived from Narita, Japan, in the early morning when the temperature was around freezing. I Googled for “What is the average temperature in January in Narita Japan?”, and got a web-page which said, among other things, “Narita has a warm humid temperate climate with hot summers and no dry season.“ and "The month of January is characterized by gradually falling daily high temperatures (to about 30°F), with daily highs around 48°F throughout the month, exceeding 56°F or dropping below 41°F only one day in ten".

So was this aircraft regularly going to and fro from an area “with no dry season” to one with freezing conditions?

[syseng68k]

Current is the problem.
Exactly, but yet another to add to the list :rolleyes:. Looking at the figures,
a cell with greater ampere hour capacity might have been a better
choice. I wonder how many discharge / charge cycles these batteries
would experience per week and in particular, how many cycles for the
replaced batteries and those that failed ?. Fast discharge / charge
cycles do have an affect on cell aging and overall lifetime.

Designers must always interprete data sheet values. Not everything is
specified in the data sheet, but if
the cell data only graphs discharge curves up to 250 amps, then they
are implying that that rate is the maximum they have envisaged for
the component, even if the absolute limits are higher. Any half way
decent design would work well within those limits, but it seems not
in this case, or am I missing something ?.

Just to be sure that I understand your post, are you suggesting that
the inverter may have been limited to taking something like 375A max.
and was able to start the APU in 35 seconds with this limitation?
(I know nothing about APUs.)
An apu is just an engine driven generator, with starter motor. In
this case, the starter motor is dual purpose and acts as a generator
once the engine is started. Iirc, it's a 3 phase ac machine and starting
works by applying ac to the windings. In starter mode, the AC supply
comes from the battery via a dc to ac inverter, which is software
controlled to provide a current limited ramp up of power to the
motor. I dont have the figures, but the inverter dc input current will
be limited to a safe value to protect the motor, inverter and battery
from overload...

[green granite]

I wonder how these people are getting on with their batteries:


The World's Largest Lithium-Ion Battery Farm Comes Online - Forbes (http://www.forbes.com/sites/uciliawang/2011/10/27/worlds-largest-lithium-ion-battery-farm/)
;

[Joetom]

Just viewed the Boeing fix, very nice.

I know they are trying to cover all the bases and did a good job I think.

Two big points from my take on it.

1. Batts are not reqd during flight.

2. Safety box to be fitted anyways.

I think there are well covering the future when any batt fails that it's no problem at all. Apart from batt not avail for use.

I think they are doing a god job indeed.

I hope no 787 batt ever smokes again, but if they have a high failure rate, regulators will insist on more changes/ETOPS problems etc etc.

Batt or any problems with the 787 will make too much press over the next few years, that will have its own problems to be dealt with.

If they have any smoking batts in the box events, it will be interesting to see how the press is handled.

I guess they have learned a lot, toned down batts and made good changes to the overall system to keep it chilled and for it to be isolated when the computer says "not normal"

So two big items remain.

1. To get the batt fix certified.

2. Checking other systems on the 787 were certified using a correct process.

I wish the 787 good fortune...

[inetdog]

Airsafes:
Heat and smoke are the first signs of a thermal runaway, once one cell starts to overheat, if the battery is not cooled by quenching the other cells will quickly follow suit. The bigger the battery the more cells.

Remember, to avoid confusion and unnecessarily scaring the public, when discussing situations like yours, we must qualify the words "thermal runaway" with either "cell" or "battery" because Boeing has chosen to use "thermal runaway" ONLY to refer to "aircraft thermal runaway" in which the end result is destroying the plane.
When they say that thermal runaway can only result from overcharging, they are using their definition of thermal runaway.
So the two accidents involving 747 cargo craft were probably what Boeing would call thermal runaway, (although as I understand it that has not been proven.) The two 787 incidents were not. :ugh:

[syseng68k]

we must qualify the words "thermal runaway"
Absolutely. Sounds like Orwell's Newspeak, where some words vanish from the
dictionary and others take on entirely new meanings :suspect:.

If those batteries didn't suffer from thermal runaway, then what was it ?...

[inetdog]

syseng68k:
If those batteries didn't suffer from thermal runaway, then what was it ?.

It was two sequential occurrences:
1. "Cell thermal runaway" in one cell, followed by
2. "Battery thermal runaway" as it spread to other cells.
Fortunately "aircraft thermal runaway" (otherwise to be known only as "thermal runaway") did not occur as a result.

PS: The above is what I feel to be an accurate paraphrase of the descriptions given during the 1 1/2 hour Boeing webcast from Japan.

You are clearly an ungood, or maybe even plus-ungood Newspeaker. :=

[ITman]

So bench testing is superior to flight testing and associated ground handling..?

Flight Global:

Boeing's certification plan, which was approved two days ago by the US Federal Aviation Administration, calls for hundreds of hours of laboratory testing and a single flight test to validate the systems.

"That will be the extent of flight testing," says Mike Sinnett, Boeing 787 chief project engineer. "It's not an extensive flight testing programme."

[fgrieu]

Quoting the NTSB report
http://www.ntsb.gov/investigations/2013/boeing_787/interim_report_B787_3-7-13.pdfBMU1 monitors for cell overcharge, overdischarge, overheating, and imbalance; controls the cell balancing function when any cell reaches a predetermined threshold; and is the source of voltage for the BCU. BMU2 provides a redundant monitor for cell overcharge. BMU3 controls the contactor and provides additional monitoring for battery and cell overcharge. BMU4 monitors for cell overdischarge and high current charge. If any of the battery monitoring thresholds were exceeded, the BMU was designed to send a signal to the BCU to discontinue charging. The BMU main circuit card and sub-circuit card do not contain nonvolatile memory (NVM), and none of the BMU data are recorded on the FDR.
So if it is not stored in NVM, nor recorded in the FDR, where does the data about cell overdischarge goes?

[Ian W]

ITman
So bench testing is superior to flight testing and associated ground handling..?

Often it is. In flight tests the testing is constrained to nominal (normal) usage of the systems they can be pushed to the edge of normal but cannot be exception tested.
In ground testing with all the aircraft systems running - Boeing has test bays with all the production level systems connected but in labs on the ground - the test script can include failures of all types in any areas required . A multi-rotation flight series can be accurately emulated for a baseline then failures of various systems added to more repeated runs. Some of these failures may be impossible to trigger in a flying aircraft or 'catastophic' so dangerous to implement in an airborne aircraft. Even pressure and temperature changes cannot be run in a controlled script in a live aircraft.
Overall the more controlled certification level testing is far more efficient and complete in a ground test than in an unpredictable and limited air test.

[EEngr]

Ian W (http://www.pprune.org/members/161813-ian-w):

Overall the more controlled certification level testing is far more efficient and complete in a ground test than in an unpredictable and limited air test. Exactly. I'm hoping that Boeing/Thales/GS Yuasa/Securaplane will continue lab testing until the nature of these failures and the battery system characteristics are fully understood.

Unfortunately, I suspect that once Boeing gets the fireproof box solution certified, the battery problem will be put on their back burner (figuratively). The knowledge gained could be used to produce a better design for the next derivative or model.

[Kiskaloo]

@EEngr
Unfortunately, I suspect that once Boeing gets the fireproof box solution certified, the battery problem will be put on their back burner (figuratively).

I expect Boeing won't be in a position to wipe their brow and sit back and relax.

The failure rate of batteries once returned to service will need to return to the one-in-a-billion chance per flight hour as I believe that is the certification requirement.

Also, as it appears a failure of the APU battery triggers a failure of the APU, if the APU battery keeps failing at what is considered too high a rate, the 787 will not be able to be certified beyond ETOPS-180 and that is going to cripple it with operators like QF, NZ and others who were planning ETOPS-240 or ETOPS-330 missions.

[EEngr]

Kiskaloo (http://www.pprune.org/members/406529-kiskaloo):

The failure rate of batteries once returned to service will need to return to the one-in-a-billion chance per flight hour as I believe that is the certification requirement.Perhaps not if the fireproof box reduces the criticality of the failure. If it can be demonstrated that it is safe to continue flight with a smoldering battery, then the 10E-9 per hour requirement can be reduced. Of course, this depends on whether Boeing will demonstrate containment for some period of time vs permanent containment.

As for ETOPS, that's cutting it pretty close with probabilities. Now its not a probability per hour figure, its a probability that the battery will/will not be available during some flight beyond a range from an alternate. Which is probability per hour times that range (in time). The difference between no ETOPS (a 30 minute diversion range?) to ETOPS-330 is 11:1. Cutting probabilities that close is a dangerous game. In other words, if you can't tolerate the APU battery loss with a 330 minute diversion, you can't for a 30 or 60 minute diversion either. Which pretty much means no flying. On the other hand, if the RAT provides a non-time limited critical power source, then the APU is not a factor anyway.

Same thing goes for the main battery. Look at its braking function. That is a non-time dependant requirement. No matter how long the flight, you need the same braking power at the end. If the probability of failure during a 330 minute diversion is intolerable, then a factor of ten isn't going to buy you more safety.

[glad rag]

What happens if BOTH batteries start to smoulder?

[Speed of Sound]

http://www.boeing.com/787-media-resource/images/graphics/Infographic-787Battery-English.jpg

If the schematic of the BMU wiring harness is accurate, then apart from beefing up the design, there is no change in the data sampled i.e. 8 x voltage and 1 x temperature.

[inetdog]

EEngr:
Same thing goes for the main battery. Look at its braking function. That is a non-time dependant requirement. No matter how long the flight, you need the same braking power at the end. If the probability of failure during a 330 minute diversion is intolerable, then a factor of ten isn't going to buy you more safety.
I have not seen it in writing, but the discussion in the Webex seemed to imply that for a plane which is landing the brakes can be powered from the RAT or some other short duration battery, and that the ability to brake using the main battery is only needed when the aircraft is being towed on the ground with neither engines nor APU running.
The APU battery is more significant, since it appears that, regardless of other power sources, loss of the APU battery will render the APU inoperable. I would imagine that taking off with the APU battery inop would not be allowed.

[msbbarratt]

@fgrieu,


So if it is not stored in NVM, nor recorded in the FDR, where does the data about cell overdischarge goes?

Presumably notable events are input to the aircraft's on board diagnostics system and maintenance logger (there's probably correct words for that kind of thing that I don't know).

As an electronics engineer I find it astonishing that the battery management systems don't retain a running log of the battery's operating conditions and status. It's trivial to do that sort of thing, and that sort of data is invaluable when you have problems like this. You'd have to be spectacularly unimaginative or tight fisted not to design that in, especially as it would cost $1.50 in parts to do it.

@ITman

So bench testing is superior to flight testing and associated ground handling..?

It can be, but it depends on knowing what the full range of possible operating conditions are, including severe extremes caused by other problems (eg loss of bay heating). I suspect that Boeing and partners have a rough idea on what those are, but it smells like they've not got many measurements or logs of what they actually go through. What's the bet Boeing lost some ancient battery specialist from the payroll and didn't replace him/her?

That in turn suggests that the spec for the battery was drawn up incorrectly, which is going to be down to a lack of experience on someone's part. That is an assumption backed up by everyone being mystified as to what's going on. The batteries are passing their existing bench test, but that's clearly not thorough enough. Anyway Boeing seem to want to fly the thing just once. That's hardly likely to fill in any knowledge gaps; only sustained operational use with full logging of everything will reveal what's going on.

Thing is, they've changed things. And worse still commercial pilots are going to be very wary of the battery, so they're going to make as little use of it as possible. It might be that the causal conditions don't arise again, meaning that Boeing may never learn what the problem actually is. And that will always leave a nagging doubt about the whole aircraft.

[Capetonian]

This was sent to me this morning and I thought it might be of interest. It does not reflect my views (quite the opposite in fact) and I am not endorsing it in any way :

Info. about the Boeing 787 Dreamliner by Boeing engineers

The guy who wrote the following is retired from Boeing.
Thought you might find it interesting...... sorta "insider stuff"......
--------------------------------------------------------------------------------------------------------------------------
For one thing the problem may not be with the batteries themselves,
but with the control system that keeps the charge on them at a given level.
And the 'battery problem" is just one problem in many.
Last week I had my regular monthly lunch with 5 fellow Boeing engineers (all but one retired)
and we talked at length about what we call the "nightmare liner". We all agreed we will not book a flight on one.
The one engineer still working (at age 74!!) says the news from inside is not good,
and that there are no quick fixes for the multitude of problems that the 787 has.
The disaster began with the merger with McDonnell-Douglas in the mid-90s.
The McD people completely took over the Board and installed their own people.
They had no experience with commercial airplanes, having done only "cost-plus" military contracting,
and there are worlds of difference between military and commercial airplane design.
Alan Mulally, a life-long Boeing guy, was against outsourcing as President of Boeing Commercial Division,
but instead of making him CEO after he almost single-handedly saved the company in the early 90s,
the Board brought in Harry Stonecipher from McDonnell-Douglas, who was big on outsourcing.
Stonecipher was later fired for ethics violations, and then the Board brought in Jim McNerney,
a glorified scotch tape salesman from 3M and big proponent of outsourcing, to develop the 787.
(Alan Mulally left to become CEO of Ford and completely rejuvenated that company.)
McNerney and his bean-counting MBAs thought that instead of developing the 787* in-house*
for about $11 billion, they could outsource the design and building of the airplane for about $6 billion.
Right now they are at $23 billion and counting, three years behind in deliveries, with a grounded fleet.
That's typical for military contracting, so McNerney and the Board probably think they are doing just fine
. But it will destroy Boeing's commercial business in the same way McDonnell wrecked Douglas when
they took over that company decades ago.
Boeing had a wonderfully experienced team of designers and builders who had successfully created
the 707, 727, 737, 747, 757, 767, and 777 in-house, always on-time,
and mostly within budget, and with few problems at introduction.
That team is gone, either retired or employed elsewhere.
(I took early retirement after the McD takeover of Boeing because I knew the new upper management team was clueless.)
The 787 was designed in Russia , India , Japan , and Italy .
The majority of the airplane is built outside the US in parts and shipped to Seattle and Charleston for assembly.
*Gee, what could possibly go wrong? * Answer: just about everything.
Because the McD people that now run Boeing don't believe in R&D, the structure of the airplane will be tested *in service*.
Commercial airplanes in their lifetime typically make ten times as many flights and fly ten times as many flight hours as military airplanes,
so the argument that composite structure has been "tested" because of the experience of composite military airplanes is just so much BS.
So structure is a big issue. The airplane is very overweight.*
The all-electric controls have the same lack-of-experience issue that the structure has.*
The only good news for me is that the Boeing pension plan is currently fully funded,
although it may not stay that way as the 787 catastrophe develops.

[Pub User]

inetdog

The APU battery is more significant, since it appears that, regardless of other power sources, loss of the APU battery will render the APU inoperable. I would imagine that taking off with the APU battery inop would not be allowed.

Not so, the APU Battery is a Cat C MEL item; without it the machine can fly, as long as the Engine Generators are working normally, but is restricted to 180 mins ETOPS.

[TURIN]

Capetonian

I've seen that 'email' pop up a few times across various internet boards now.
I suspect it's a hoax with a few grains of truth attached.

We'll see.

[cockney steve]

Overall the more controlled certification level testing is far more efficient and complete in a ground test than in an unpredictable and limited air test.

As demonstrated by a new model released to service,which has such major incendiary problems that the entire fleet is grounded?

Sure does inspire confidence.....NOT

[Ian W]

CockneySteve
Quote:
Overall the more controlled certification level testing is far more efficient and complete in a ground test than in an unpredictable and limited air test. unquote

As demonstrated by a new model released to service,which has such major incendiary problems that the entire fleet is grounded?

Sure does inspire confidence.....NOT Steve - a word in your shell-like...

You are conflating the scenarios used in the original testing with the capabilities and limitations of ground testing. The original test scenarios obviously did not cover the failures that have occurred, but included a lot of flight testing. This is a limitation of the scenario writers and approvers not of the ground or air testing. A full set of scenarios and test cases that requires extreme failures of systems can only be run successfully on the ground. The aircraft testing can only be of standard battery performance and this nominal testing is just as easy on the ground.

The one area I would test in a live aircraft is having airline first line maintenance and push crews do repeated 'turn around's and routine towing with one of the 'spare' 787s currently clogging Everett. If the FAA would allow it fly a 787 on multiple short rotations and ground turn arounds. While that was happening I would watch the ground crews and see what they really did as opposed to what they say they do and people expect them to do. I suspect that something in the ground handling is unexpected. Does the ground crew safety man ride the brakes running down the main battery when the aircraft is towed? Do they routinely leave nav lights on running down the battery(ies), do they open the electronics bay door and leave it open which on frosty nights could let batteries get too cold etc.

One thing that you can be sure of is that Boeing is very very aware that if one of these batteries causes even a minor problem in the next 5 years the 787 may go the way of the Comet which would be devastating for the company. So they have nothing to gain and everything to lose if these tests are skimped.

As it is, the 787 will be one of those aircraft that is repeatedly pilloried by 'the trade media' in the same way as the Harrier (until the Falklands) and the Osprey - until it went 'live' in action.

[EEngr]

Ian W (http://www.pprune.org/members/161813-ian-w):

The one area I would test in a live aircraft is having airline first line maintenance and push crews do repeated 'turn around's and routine towing with one of the 'spare' 787s currently clogging Everett. If the FAA would allow it fly a 787 on multiple short rotations and ground turn arounds. While that was happening I would watch the ground crews and see what they really did as opposed to what they say they do and people expect them to do. I suspect that something in the ground handling is unexpected. Does the ground crew safety man ride the brakes running down the main battery when the aircraft is towed? Do they routinely leave nav lights on running down the battery(ies), do they open the electronics bay door and leave it open which on frosty nights could let batteries get too cold etc. That's all good information to have. But that's not the place to capture it. The ground crews know that they are being watched and will work to the rules.

The best way to capture this sort of thing is to have good relationships between customers operations and Boeing engineering. Good enough so that the customer people can tell Boeing (without the risk of word coming back to bite them) the way things really work out on the flight line.

We learned far more in engineering by walking the factory floor and speaking to the mechanics building the things. Back when we had engineers that were not afraid of getting their MBA suits dirty, that is.

[TURIN]

That's all good information to have. But that's not the place to capture it. The ground crews know that they are being watched and will work to the rules.



Spot on Sir. :ok:

[Ian W]

Yes they will know they are being watched and yes they will work -to the rules-. However, that in itself will throw up areas that the writers of the rules did not expect. Where the experts who wrote them always did something because they always did it and didn't think to put it in the procedures. I would like to think that the turn around procedures were fully checked initially and when the aircraft was handed over that the procedures on site were fully checked as part of the training. But 'like to think' is an assumption that is often unsafe. Even showing that when the procedures are followed repeatedly the problem does not occur is a useful result. I emphasize repeatedly because that repetition may not have occurred during normal testing.

I think that rather in the way there are fatigue test rigs that keep ahead of the aircraft in fatigue life to identify weak spots, perhaps battery fatigue rigs are needed that emulate a day in the life of a hard worked battery with all the pressure, temperature, charging and discharging cycles running at worst case.

[Volume]

I think that rather in the way there are fatigue test rigs that keep ahead of the aircraft in fatigue life to identify weak spots,It is however quite usual to find cracks on the in-service aircraft which have not yet occured (or even will not occur during the whole test), simply because the test conditions do perfectly match the design requirements, but unfortunately not the real operational life... There have always been surprises, there will allways be surprises. That´s why we design and test with safety margins and second lines of defense.
So unless we find a production quality issue to be the cause of the failure(s), clearly the tests were not simulating real life. This can happen for new technology. So analogue to the fatigue test: add temperature cycling, environmental exposure etc. to the test, and you may obtain better results. Experience however shows that we can ignore these effects. Unfortunately for batteries we still do not know what we have to simulate (Temperature, Pressure, Vibrations...) to have an effective test. If we test the wrong conditions, it does not help if we are far ahead of the real fleet with respect to simulated flight hours. It is easy to add costs to a test by adding new aspects. It is hard to add relevance to a test...

[Ian W]

You are correct that fatigue tests do not always show up what fails in real life but that does not mean that they are not useful to highlight areas of weakness that will show up. It would be a good thing to do anyway with an over-insturmented set of batteries to increase knowledge of the effects of continual cycling.

[kilomikedelta]

EEngr: Your last sentence is descriptive of 21st century reality. The previous sentence described 20th century reality. Perhaps the recent number of dud aircraft projects could be correlated to the ratio of engineers who go on to get an MBA with respect to the number of MBA's who go on to obtain an engineering qualification.

[PickyPerkins]

Before ANY test flight(s), as a simple member of the public I think it would be reasonable to see at least something along the following lines.

I understand that two of the first 787 airframes were written off.

I would expect one of these airframes to be fitted out with the new battery containment system, complete with its fully charged battery, with visible and infra-red cameras and video cameras both inside and outside the airframe.

On the ground, bring about the most sudden run-away possible in the battery and let the world see what happens.

Only after that should any test flight be permitted.

Safety is not concerned with any theory of how failure occurs, or with any statistics of probability of failure, but only with the consequences of a run-away, which someday, somewhere, will occur.

What argument could be put forward against this proposal?

[FlightPathOBN]

Boeing has already identified 2 airframes for testing...both are recent builds, one already slated for a new engine design testing (??)

[Ian W]

PickyPerkins

See Business jet will have sturdier batteries than Boeing 787 | Business & Technology | The Seattle Times (http://seattletimes.com/html/businesstechnology/2020241162_787battery29xml.html)

That is precisely what Cessna have done for the new Citation which will have smaller but similar Li-ion batteries.

A video shows what happened when engineers disabled all the battery’s protective systems, overcharged it and then deliberately ignited the hot chemicals: Nothing more than a few wisps of smoke puffed out of the battery box.

Boeing cannot afford to skimp on these tests

[PickyPerkins]

And the FAA cannot afford to skimp on these tests if they want to retain the confidence of the public.

[Pub User]

On the ground, bring about the most sudden run-away possible in the battery and let the world see what happens.

I believe they have tried this as part of the investigation process, but were unable to achieve any significant run-away.

[PickyPerkins]

Did they try a short-circuit on the battery?
Wouldn't that release all the stored energy in short order?

[inetdog]

PickyPerkins:
Did they try a short-circuit on the battery?
Wouldn't that release all the stored energy in short order?
I believe that they tried an external short circuit of one cell, and I know they tried an internal short circuit (nail) of one cell.
I think that in both cases the cells were not in closed battery case with other cells when they tried it. It has also been observed since then that because of contact area, contact resistance, and electrode resistance problems a nail may not actually be a worst case internal short. It also immediately vents the cell!
A short circuit of the entire battery might not be a worst case either compared to thermal runaway. To get 900 amps from the battery, you have to use something close to a short circuit anyway.

[Machinbird]

Just speculating here............with regard to the original 787 battery design.
Probably the easiest way to overstress a battery cell, without this being detected by the battery monitoring unit would be to lose the electrical contact with one of the plate sets within the battery cell itself.

Seems to me that this would force the remainder of the cell to attempt to carry the load or to accept the charge being applied to the rest of the battery cells during charging.

Basically the same effect as substituting a lesser capacity battery cell in series with the remainder of the battery cells. No way to avoid abusing the 'smaller' cell with the original design if that happened.

Has this been discussed elsewhere? :suspect:

[inetdog]

Machingbird (I like that one):
Basically the same effect as substituting a lesser capacity battery cell in series with the remainder of the battery cells. No way to avoid abusing the 'smaller' cell with the original design if that happened.

Has this been discussed elsewhere?
Have not seen discussion, other than the argument the the "cell" should be treated and protected as if it were three cells in parallel, or physically or virtually isolated and should be monitored and protected as such. But if the kind of failure you propose happened the result would depend in part on how much adjustment is possible within the battery balancing network. If it is working properly, that cell will not be driven below LVCO because the BMU will tell the charger that it had a problem and the battery itself would open the contractor within the battery if the load or charging did not stop.
Nor will the remaining two sub-cells be forced to take current once their voltage reaches the upper limit. That would have the effect of limiting the whole batteries performance to the low to high capacity range of that partially failed cell. The resistive heating would be slightly larger, but not enough for an thermal cascade or venting.
But that assumes that the balancer wires and pass element for each cell can carry the full ~40 amp charging current, and that is very unlikely given the size of the wires shown.
You may have a good point, and the CAT scans of the APU battery showed some internal collector wire to electrode disconnects within several of the cells. But that was assumed to be a result rather than the cause of the failure. Some of the 1/3 cell rolls did look different from their neighbors.

[FlightPathOBN]

This extract from a Boeing video shows a severe test of the proposed 787 battery containment enclosure. Propane gas ignited inside the box explodes. The 1/8th-inch thick steel walls bulge out but hold fast.
787 Battery Tests | Video | The Seattle Times (http://video.seattletimes.com?bcpid=30884189001&bckey=AQ~~,AAAAAFn2Wfk~,QUqnr01qM6aNyA1l3Tnqn9EkxU1YnZwX&bclid=0&bctid=2245764552001)

Interesting...during the test, look at the expansion, it appears to be contained by the box the test is being run in...

[LandIT]

Do we think that containing a momentary explosion caused by the introduction of propane gas, proves anything about an effective containment of the thermal runaway reactions of volatile chemicals released as a consequence of the battery failure they experienced twice already?

I don't think it does.

And I do not feel like flying on a 787 while it has that sort of technology which has now proven itself twice to do what it was said to be "impossible" to do - catch fire. I don't ever want to fly on one of those 787's because it looks like it has a potential bomb strapped to the fuselage. I hardly want to be at the same airport as one of those things.

Boeing has really screwed up over outsourcing the risk-sharing and external design parts of that airplane. The ultimate consequent risk-share is the penalties Boeing should have to pay those airlines they promised the benefits too - benefits that now look impossible to materialise in any safe and secure way. How much maintenance is that thing going to take also?

Why any engineer would think that the acceptable way to mitigate the risk of a runaway chemical reaction and consequences is by the containment of that fireball in a stainless steel housing for an hour while the plane attempts to land is beyond me. I won't be on board, that's for sure.

[Blacksheep]

The steel box is a PR disaster as well as a maintenance headache with its 52 bolts holding the lid on.

The changes in the cell manufacturing process, battery construction that includes ceramic heat shielding, new internal battery electronics and logic and a revised battery charger are the actual fix. The battery is a completely new design, but the containment box ensures that the travelling public - and many uninformed aircrew - will continue to regard the B787 battery as a highly dangerous piece of equipment. (Which the original, in fact, was)

[Kiskaloo]

LandIT
Do we think that containing a momentary explosion caused by the introduction of propane gas, proves anything about an effective containment of the thermal runaway reactions of volatile chemicals released as a consequence of the battery failure they experienced twice already?

I don't think it does.

I am sure neither does the FAA so to assume this was the only test Boeing performed is not logical.

Boeing has really screwed up over outsourcing the risk-sharing and external design parts of that airplane.

I doubt Boeing designed the Ship's and APU batteries for any of their commercial airliners. I expect every one of them had their design and production outsourced to external suppliers.


Blacksheep
The battery is a completely new design, but the containment box ensures that the travelling public - and many uninformed aircrew - will continue to regard the B787 battery as a highly dangerous piece of equipment.

If those changes to the battery stop them from failing, soon enough the traveling public will forget about the containment box just as they have forgotten the nitrogen in the fuel tanks to prevent a fuel-air explosion and the armor in the nacelles to prevent a failed turbine blade from being shot into the fuselage.

[RetiredF4]

With this firebox they mask the real screwup.


Aviationweek (http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_03_25_2013_p35-561498.xml&p=2), bolding by me.

The battery will also sit on a redesigned frame containing drain holes to allow moisture to escape. In its testing, Vice President and 787 Chief Project Engineer Mike Sinnett says, Boeing found that moisture paths can lead to short circuits in cells which could lead to “stress in the cell,” or the buildup of heat and venting of vaporized electrolytes.

[PickyPerkins]

I see the same Aviation Week article says that the batteries will be "... subjected to repeated load tests of 18 kw over periods of 40-45 sec. ...". This looks like the same test originally specified in the Boeing Control Specification Document (SCD) for the battery.
http://www.pprune.org/7745740-post1009.html

The NTSB Interim Factual Report dated March 7, 2013, quoting the manufacturer, said that the operating range of this battery is 20V - 32.2V, with a "nominal voltage" of 29.6V. At this "nominal voltage", 18kW requires 608A from the Yuasa cells whose published current maximum is 375A.

Does anyone know what factor dictates this 375A limit?

Adding to the confusion, the NTSB "MATERIALS LABORATORY FACTUAL REPORT", Report No. 13-013, February 19, 2013, says on page 8-9: "Based on information from the battery manufacturer", nominal specifications for the individual battery cells include a "Maximum discharge capacity" of approximately 1000 A (though typically 450 A for ~45 seconds, when being used for APU start-up, and no greater than three attempts at start up), which is rather different from the published specification for the individual cells of 375A. And on page 4, for the contactor which is inside the battery case, "The battery design incorporates a contactor rated to 400 A", which is a lot less than the 1,000A now claimed as the battery maximum discharge capacity.

[green granite]

My guess would be the internal resistance of the battery, the rated power being the amount that keeps the cell temperature just within it's permitted level.

[PickyPerkins]

RetiredF4

I think you are on the right track in noting Boeing's remarks on moisture.

From memory, I think the statement was phrased something like, “During testing, we have learned that it is possible for moisture in the form of condensation to form a very high impedance short-circuit between the battery and the case which can lead to stress and venting of cell(s)” Not the exact words but near enough from memory.

Boeing also said that the vaporized cell contents escaping from the box “only caught fire because it came into contact with arcing wires outside the box”. No explanation as to why they were arcing, but I assume it was the ground wire which was found burnt out.

Both these events are very similar to an idea in the link below and earlier links from the same contributor:
http://www.pprune.org/7691355-post785.html

From first-hand experience I know that water will accumulate in any nearly closed container which is subjected to humidity and temperature cycles.
http://www.pprune.org/7746642-post1014.html

The Boston incident aircraft was operating between Narita, which has a daily high of about 50ºF and no dry season, and Boston, which is generally freezing in January. This particular battery had been in airline service for only 18 days and 22 flight cycles before it failed.

So I think that Boeing thinks that moisture was or could have been the likely cause of failure and that if they can keep moisture out that there will be no more early battery failures. The new enclosure is necessary for this purpose as well as to keep oxygen out and debris in.

The proposed enclosure and burst disk certainly has the potential of keeping out moisture if it is installed and maintained properly, e.g. no undetected leaks in the system.

[kenneth house]

Looking at the CT scans from both investigations you can see puffed out cell cases in the undamaged battery packs. This is an indication of overcharging in Li batteries.
Looking at the Secura patent for battery charging you will notice two things of interest. The method was based upon a Ni-Cd battery charging profile, and the procedure assumes a trickle-charging phase of indefinite end following the fast charge phase.
Looking at the FDR data from the Boston event you can see that the battery charger was indeed holding a constant 32 volts and trickle-charging the APU battery at 1-2 amps for about 17 minutes after the APU start until the fire started.
Looking at the charging process for Lithium batteries from GS Yuasa and every other Li-battery manufacturer in the world and you will find that there is no trickle-charging. Instead you will find a specific charging procedure that consists of a constant current (at ~1C) charging phase up until the cell voltage hits a specified cut-off value, then followed by a constant voltage phase in which the cell is held at this specified voltage until the current drops to C/20, at which point the cell is fully charged, charging is complete, turn off and disconnect the charger.
Looking at the data sheet for the LVP-65 cells from GS Yuasa used in the APU and Main battery packs you will find that they have a nominal capacity rating (1C) of 65 Amp-hrs, nominal voltage of 3.73, maximum charging rate of 1C amps, and the cell characteristic curves use 4.025 volts as the CC/CV specified charging cut-off voltage. The C/20 cut-off charging current is 65/20 = 3.25 amps. There is no procedure called out nor should there be any additional charging below 3.25 amps after reaching the 4.025 volt level.
Attempting to trickle-charge a Lithium battery, especially one that is already fully charged, is a sure-fire way to cause thermal runaway...

[EEngr]

kenneth house (http://www.pprune.org/members/407907-kenneth-house)

Looking at the Secura patent for battery charging you will notice two things of interest. The method was based upon a Ni-Cd battery charging profile, and the procedure assumes a trickle-charging phase of indefinite end following the fast charge phase.Interesting. The NiCd 'trickle charge' mode that Boeing employed on previous models was also referred to as the T-R (Transformer-Rectifier) mode. Basically, once the battery was charged, the charger switches to a constant voltage source, both to keep the battery topped off and to supply the few small loads always connected to the battery bus. Without this mode, the battery would cycle between a constant current charge (high speed) and slowly being drained down by these parasitic loads. Since there was a requirement to maintain a high state of charge, this could not be tolerated. The odds that, when the batteries standby capacity was needed it would be at the 'bottom' of one of these cycles, were not acceptable.

Does the 787 system have such parasitic loads? Stupid question actually, because the batteries own built in charge monitoring system is one instance. But then, does the 787 system have such a 'float' mode to avoid this state of charge cycling and the inevitable low points in the capacity curve?

Its possible that the only way to fly with a LiCoO2 is either to provide the float voltage (unsafe) or to accept the lower point on the available charge curve as the 'best' avalable charge for design/certification purposes and thereby have to oversize the battery to allow for it. One would need to peek inside the head of the systems engineer responsible to know how this decision was made, I'm sure.

[Ian W]

EEngr

Does the 787 system have such parasitic loads? Stupid question actually, because the batteries own built in charge monitoring system is one instance. But then, does the 787 system have such a 'float' mode to avoid this state of charge cycling and the inevitable low points in the capacity curve?

Its possible that the only way to fly with a LiCoO2 is either to provide the float voltage (unsafe) or to accept the lower point on the available charge curve as the 'best' avalable charge for design/certification purposes and thereby have to oversize the battery to allow for it. One would need to peek inside the head of the systems engineer responsible to know how this decision was made, I'm sure.

I don't quite follow the logic. The charge monitoring system should not act as a significant continual drain the battery. All other 'parasitic loads' would surely be met by the generators that would be running if the battery is being or has been charged.

It does seem that assuming that the design assumes a NiCd charging profile rather than that required for a LiCo battery is assuming that Thales and Boeing have both made a rather basic error. Do you really think that is the case?

[EEngr]

The charge monitoring system should not act as a significant continual drain the battery.Define 'significant'. While it is possible to build a microcontroller-based system that has sub-milliampere current demands, I'm not certain of the technology of the monitoring equipment inside the battery. Its possible that on the shelf it runs in a sleep mode, with a few tens of microamperes load. But when installed and communicating with the charging system and other airplane equipment, it draws far more.

All other 'parasitic loads' would surely be met by the generators that would be running if the battery is being or has been charged.On the 767 and 747-400 there are a few loads powered off the battery bus at all times when the bus is energized. Although this didn't amount to more than a few amps, it was supplied during normal operations by the battery charger's T-R (constant voltage) mode. These sorts of loads together with the battery internals are what I consider to be parasitic. That is, always connected (unless the bus is switched off) and not switched over to other sources.

This bus topology may have been carried over to the 787 from models with NiCd batteries, where floating the battery was a non-issue.

[mm43]

@Kenneth House

Your succinct description of the correct method of charging Li-ion batteries is appreciated.

However, the apparent failure of the Charger/BMU to cease charging the battery at CV (4.025V) once CC/20 (65A/20=3.25A) was reached, must have been occurring often. Deformation of the affected cells must also have been occurring incrementally throughout those periods. So that begs the reasoning behind Boeing's destructive test program, which if followed to the letter, has failed to take account of compounding cell deformation over a longer period.

Page 33 of the NTSB's Interim Factual Report includes the following Boeing test procedure for FAA approval -
Battery testing consisted of full-performance, environmental qualification, and destructive tests. The destructive tests included external short circuit (low and moderate impedance shorts at battery terminals), overcharge (charge battery at 36 volts for 25 hours), high-temperature storage (185º F for 18 hours), and over-discharge (discharge battery to zero volts) tests. Boeing indicated that the tests found no evidence of cell-to-cell propagation failure or fire.Note that no mention of any cell deformation is made, rather NO "cell-to-cell propagation failure or fire" met the spec..

[RetiredBA/BY]

Kenneth House,

You mention a cutoff voltage of 4.025 v should that not read 4.25 v?
Or is it that 4.025 is chosen as a safety buffer from the absolute maximum lithium voltage of 4.25?

[kenneth house]

@RetiredBA/BY

The characteristic curve graph on page 2 of the LVP65 datasheet indicates 4.025 volts. i would attach an image showing this but don't seem to have image upload privileges.


@mm43

i did see that statement in the report about passing an overvoltage charging test and was quite puzzled. i would love to see that test data. So far i am at a loss to understand or explain how the battery could survive a 36-volt overcharge (4.5vpc) for 25 hours without seeing the corresponding current profile--voltage without current is meaningless.

On page 21 of the latest JTSB report there is a graphic showing both battery and cell voltage ranges for the 4 BMUs. i have not translated it yet but it shows some captions at the 36.5 volt pack level and also for the 4.55 volt cell level.

Could it be that the contactor opens when the terminal voltage exceeds one of the BMU limits on the high side just as it does at the low side? -- in which case the 36 volt overcharging claim is a legally true statement, but lacks technical integrity.

Why the curious 25 hour limit? A 2.6 amp contactor coil current would use up the entire pack capacity in 25 hours (2.6 x 25 = 65 Amp-hrs), in which case the contactor would return to it's normally closed position and a large potential would be applied across the depleted cells with a huge charging current exceeding 1C.

i have taken thousands of laboratory measurements of voltage, current and temperature on several dozen lithium iron phosphate (3.2 v nominal) cells while under high-rate (1C) charging and discharging. Even though the Yuasa cells are a different chemistry, i am quite certain that a true 36 volt charging condition (4.5 volts per cell) would rather quickly be spectacular to watch from a suitable bunker.

[green granite]

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

Interesting series of posts by the way. :ok:

[FlightPathOBN]

From Boeing Land..

Interesting just how many panels have roasted, unrelated to any battery issues of course!

UPDATE: Boeing 787 flight test postponed (http://seattletimes.com/html/businesstechnology/2020671693_boeingtestflightxml.html)
A planned Boeing 787 Dreamliner flight to test new power panel engineering was postponed Saturday

[mm43]

@Kenneth HouseWhy the curious 25 hour limit? A 2.6 amp contactor coil current would use up the entire pack capacity in 25 hours (2.6 x 25 = 65 Amp-hrs), in which case the contactor would return to it's normally closed position and a large potential would be applied across the depleted cells with a huge charging current exceeding 1C.Perhaps we need to look more closely at how the contactor is being controlled via BMU/Charger interaction. I note your neat deduction of the contactor coil current, but suspect there is some "smoke and mirrors" involved in its operation. Could well be that the contactor physically latches in the open position and a low current control circuit trips the latch when it is required to return to the NC position. The BMU detects the Charger over voltage condition and either opens the contactor or prevents it from closing.

If the above is the case when applying the over-voltage test, then you are correct, the only condition fulfilled in such a test was the ability of the Charger/BMU to prevent an over-voltage charging condition, effectively indefinitely. To apply 36V to the battery without any BMU involvement would IMHO certainly result in thermal runaway.

[A4]

McNerney also said that Boeing was taking the opportunity of the battery fix downtime “to tighten up some things and make sure we’re in good shape as we get this plane back into service.”

:confused:

Is this supposed to inspire confidence in the product? :ugh:

[cockney steve]

TRANSLATION

"While attention is diverted elsewhere, we'll rectify some of the other deficiencies before they bite us on the ass as well"

[ITman]

The other problems appear to be the power panels...!

[FlightPathOBN]

Sorry about the link...the Seattle Times has gone to some crap subscription program.

The items in the article elaborated on the issues with the power panels, and gave more detail of several flights, including ferry delivery flights, that had to return due to error messages in the flight deck. Panels were found to have shorted out, with one charred.

There is of course, the story regarding the panel 'fire' on flight test..

A failure in the P100 electrical panel of Boeing’s second flight-test 787 Dreamliner led to Tuesday’s fire, which involved an insulation blanket, Boeing said Thursday.

The company said it was still investigating how the incident happened and what steps might be needed before returning 787s to flight testing.


“We have determined that a failure in the P100 panel led to a fire involving an insulation blanket,” Boeing said. “The insulation self-extinguished once the fault in the P100 panel cleared.

“Damage to the ZA002 P100 panel is significant. Initial inspections, however, do not show extensive damage to the surrounding structure or other systems. We have not completed our inspections of that area of the airplane.”

Boeing has removed the panel and nearby insulation material and is sending a replacement panel to Laredo, Texas, where the jet landed Tuesday, the company said.

The panel receives power from the left engine and distributes it to aircraft systems. Backup systems — including power from the right engine, the Ram Air Turbine, the auxiliary power unit or the battery — are designed to automatically engage in such incidents and did so Tuesday, allowing the crew to maintain positive control of the airplane and land it safely, Boeing said.

“Molten metal has been observed near the P100 panel, which is not unexpected in the presence of high heat. The presence of this material does not reveal anything meaningful to the investigation,” Boeing said.

Inspection of the surrounding area will take several days and is ongoing. It is too early to determine if there is significant damage to any structure or adjacent systems.

As part of our investigation, we will conduct a detailed inspection of the panel and insulation material to determine if they enhance our understanding of the incident.
We continue to evaluate data to understand this incident. At the same time, we are working through a repair plan. In addition, we are determining the appropriate steps required to return the rest of the flight test fleet to flying status.

[kenneth house]

According to the NTSB Airworthiness Report on page 37:

The contactor is identified as part number 104CZ02Y01 from the French company Zodiac Aerospace. It is a normally-closed solenoid with single-pole single-throw contacts and does not have a latching feature. On page 32 it states that
the contactor is normally closed and was designed to open in the event of an overcharge situation.

Also from the same report on page 32 is some description of the battery monitoring unit (BMU):

In the event that monitoring thresholds are exceeded BMU1 and 2 will send a signal to the battery charger unit to discontinue charging (overcharge and over-discharge monitor).

BMU3 contains controls for the contactor and provides further monitoring for battery and cell overcharge.

BMU4 monitors for cell over-discharge, high current charge, and contains inhibitions signals that will latch in the event of an over-discharge or a battery high current charge.

In the event that the monitoring thresholds are exceeded, BMU3 and 4 will send a signal to the battery charger unit to discontinue charging.


There was mention in the report that the contactor had dual coils, but i have not found a datasheet for the device to see the electrical schematic.

[syseng68k]

kenneth house:


There was mention in the report that the contactor had dual coils, but i
have not found a datasheet for the device to see the electrical schematic.
Can't say for this one, but it's quite common for contactors of high
rating to have dual coils. The contact pressure required needs a strong
spring to keep contact resistance low, which in turn needs high magnetic
field strength to operate against the spring. The first coil is low
resistance, high current to close the magnetic circuit, while the second
or holding coil is much higher resistance and is enabled by an auxilliary
contact. Typically, the two windings would be in series at rest, with the
high resistance winding shorted out, then unshorted as the solenoid
operates.

There was some discussion of the contactor earlier in this thread.
Post #902, for example...

The really worrying thing is that the battery subsystem appears to have
been designed on the assumption that the cells would never leak electrolyte.
If they do, then the bmu boards are quickly toast. The contactor, which
is driven from one of those boards, may never operate, leaving the
battery connected as it self destructs.

I wonder if the long term fix will be to put the boards in a sealed
enclosure within the box, or will they fudge that as well ?. Until there's
more detailed info on the solution, there can be little confidence that
they have done it right. An armoured box doesn't qualify as a solution, imo,
though presentation often wins over substance these days, it seems ...

[mm43]

@ Kenneth HouseThere was mention in the report that the contactor had dual coils, but i have not found a datasheet for the device to see the electrical schematic. Likewise, my search for any info on Zodiac Aerospace electrical data has also drawn a blank.

Thales, as the main contractor appears to have a large number of sub-contractors under its wings. OEMServices seems to be the umbrella vehicle, and Meggitt, Securaplane and Zodiac Aerospace provide the expertise which Thales has sold to Boeing.

The split high/low resistance solenoid winding as detailed by syseng68k would appear to equate to the dual coil mentioned by the NTSB. I suspect that quite some more detail will be revealed when the NTSB undertakes its public investigative hearing (April 23-24) into how the Li-ion battery/charger came to be approved.

The following from the Thales Group website -Thales offers an innovative and highly secure Li-Ion emergency low voltage system for commercial aircraft. It is the first commercial application of Li-Ion technology anywhere in the world. Thales Li-Ion sub-system comprises:
- a Li-Ion battery
- a Li-Ion an[sic] Ni-Cd battery charger. - may yet prove to be an embarrassment to not only Thales.:ouch:

[Old Engineer]

I spent the late hours of last night reading the entire corporate page of ZodiacAerospace (it was an e-copy of their annual report). Zodiac apparently made the Zodiac boats that Cousteau was always speaking of. These had flotation sides that were tubes of cloth-covered rubber material. Fast forward and Zodiac Aerospace is making large numbers of aircraft seats, with knowledge of how to affix cloth to a rubberized backing with rubber cement a key factor here, receiving much attention.

At some point, ZA appears to have acquired a company they made into a division called ECE (could not discove its antecedent name). ECE made one major product (taking the single product mentioned in the annual report), namely "contactors". ECE, with the backing of ZA, widened its line to aircraft electrical distribution systems, including panelboards, and some high intensity LED cabin llighting.

ECE now seems to be principally manufacturing in Tunisia (certainly their contactors). Cabin seats are manufactured in several countries (not France), of which Tunisia is one of ZA's larger producton locations.

So ZA began as a maker of rubber boats, and Boeing began as a maker of aircraft. I recall that certain Rolls-Royce turbines of great output had turbine shaft bearings make by a German supplier who had been a maker of motorcycles.

In the matter of the matter of the contactor part number, I think the whole part number would have to be something like "Contactor, aircraft, 104CZ02Y01". The number form has tripped a dim memory-- it seems to derive from the [US] Federal Specification system which saw such developement in WWII. So, 104C identifies the basic contactor wanted, and Y01 is an add-on set of repeating contacts (the Y01 is what I remember ...IIRC of course).

I forget what Z02 was, but it's some sort of add-on device that could also be ordered preinstalled. The repeating contacts would confirm to the supervisory system board that the contactor had actually moved as commanded. I forget what Z02 was, but I want to say Z was for locks. On one job where there were a lot of these puppies (GE had beautiful and massive slick paper catalogs of all this good stuff), I recall on a double-end substation, we had a load bus divided in the center (by some distance), so we had three large breakers (1200 amps) locked by special keys-- only two nonreproducible keys. So the power sources could not be interconnected; also the phase cable across the center separation were additionally protected by cable limiters (a type of fuse) at one end.

This all sounds OT, but it is exactly the configuration of the two battery souces in the 787. Or should be-- that is why I am puzzled that someone said the forward battery could assist the APU battery in starting the APU. Well, of course its DC and you have that diode isolation (that never shorts through, of course). Not at the same time, I hope.

You could also get field kits for more elaborate add-on functions, but these were not available factory-assembled. Possibly mechanical latches or blocking devices were in this category. One thing I recall was an electric drive to reset the bigger breakers, otherwise a crank was used.

So who knows what this contactor situation really was?

OE

PS-- What is the difference between the battery bus and the hot battery bus? :)

[3holelover]

OE. The hot battery bus is "hot", or powered, even while the battery may be switched off. Not so with the battery bus.

[kenneth house]

@ OE, syseng, and mm

Thank you all for the good zodiac research and explanations about the contactor and the second coil/auxillary contact. i tried to sign up on their customer support site to download technical info but haven't been given access yet.

In the latest JTSB report on page 10 is a schematic showing the Hot Battery Bus (HBB) downstream of the Bigass Diode Module (BDM) on the Main Battery positive terminal. The HBB connects to the Captains 28V DC Bus (CAPT) thru the Main Battery Relay (MBR). What is operational function and criticality of the Captains Bus?

Also does anyone know if the FDR data for the ANA/Japanese event is available online similar to that found on the NTSB docket for the Boston event?--it would be interesting to see what the Main battery current signal shows before and while the pack was shorted to ground thru the case.

i thought it was an interesting finding by JTSB that cells 4 and 5 in the Main pack were basically intact with no broken current collectors inside and the pressure relief valves had not opened, unlike cells 1-3 and 6-8.

Some of the lithium battery experts in the electric car world have set up trickle charging experiments to determine how long it takes for a cell to go thermal from overcharging--but none are yet using a LVP-65 Yuasa cell.

[Old Engineer]

@3-HL Thanks for the answer. The "Hot Battery Bus" I would think of as the "tie bus." A tie bus was usually broken in the center, but kept powered from either end with the load roughly divided in half. The tie could only be closed if one of the sources was open. The double ends were sourced from two independent power company lines. They are a bit unusual, and at the customer level usually operated manually.

How's that song go... "Ya gotta know the jargon..." No, "territory." OE

PS-- GE offers only mechanical latching at 400 amps and up. It's electric release of latching. Of course, that's 3-pole stuff from GE. Below 400, latching comes as a kit, field installed, with a separate part number and price.

[Old Engineer]

Hamilton Sundstrand is the maker (possibly European sales use a different source) of the alternators driven by the 787 APU. These are 225 KVA units (each; I put that = 180 KW) intended to have a phase to phase voltage of 230. That make the phase current about 600 amps.

Hamilton also makes the blower/compressors for cabin air. They note these as being able to operate on a variable frequency feed with a range of 360 to 800 cycles. That gives us the alternator output frequency specification. Boeing has described it as a variable freqquency system.

Hamilton also makes the turbine main engine-driven alternators. There are four of these and I believe they are also each of the save 225 KVA output. They might differ in the gear ratio to the respective turbines.

Between 1974 and 1978, the labs at Curtis-Wright, with major assistance from GE, worked to build and test a turbine-driven alternator with a rating of 150 KVA. This had a permanent-magnet rotor with salient (misspelled 'sahlen' somewhere) poles of samurium-cobalt-- 14 rotor poles and a 9-phase stator winding, cycloconverted and filtered to a well-formed 3-phase output. Curtis-W labs had earlier tested an equal-sized and similarly constructed machine which had a wound rotor (i.e. suppled with external DC).

Of interest is the rotating speed range, from 12000 to 21000 rpm (that is, within 2:1). I'll have to clearify which unit had that speed as the last report page was a errata sheet dealing with that. I will explain the significance of all these variances, down the road.

What I am looking for is if and how these components and their operating ranges might cause variation of the voltage on the "hot" battery bus. Since we have minimal system details, we can just design what major detail is missing.

For starters, a major question is whether the APU altenators have a wound-rotor design (has then to be a DC winding). Anyone know?

OE

[Machaca]

Boeing says (http://www.boeing.com/commercial/aeromagazine/articles/2012_q3/2/):

The variable frequency starter generator is a six-pole machine within an aluminum housing driven directly from the main engine gearbox. The generator is a brushless, three-phase, alternating current, and variable frequency synchronous machine. It has a nominal rating of 235 volts alternating current (VAC), 250 kVA, three phases, and 360–800 Hz output.


UTC photo shows it's a good sized lump:

http://utcaerospacesystems.com/wp-content/gallery/electric-systems/787-electric-starter-generator.jpg

[Volume]

a good sized lumpAnd the one in the background showing the wiring gives an impression what 250 kVA really means... This beast plays in a totally different league than your cars alternator.

[kenneth house]

Since it is brushless and synchronous, i.e. frequency varies with speed, it would seem to be a permanent magnet rotor machine, with 3-phase wye winding plus neutral for the stator.

Looking at the schematic on page 11 of the Airworthiness report there is a functional block diagram for some of the power distribution of the forward and aft E/E.

The starter/generator functions as a starter for the APU (using 3-phase AC?) developed in the APU Controller fed from the P49 APU Batt Elect Panel. It then functions as an alternator/generator producing variable frequency 235VAC that is collected in the P150 APU AC Elect Panel. The AC panels feed the AC busses and the TRU rectifies AC to create the 28 VDC Bus.

Four electrical busses are described: 235 vac and 115 vac both variable frequency, plus 28 VDC and 270 VDC.

i didn't see anything about how grounding is done, but i would think that all the busses are tied and referenced to chassis. In electric cars the high-voltage traction battery packs are isolated from vehicle chassis--i was surprised to find that the Main and APU battery packs have their negative terminals grounded to the airframe chassis.

[FlightPathOBN]

todays battery test flight..2 hours should be enough for approval...right? :\

http://operationsbasednavigation.com/wordpress/wp-content/uploads/2013/04/ScreenHunter_36-Apr.-05-13.26-e1365193649459.jpg

[TURIN]

Hot battery bus. As has been said, is connected directly to the battery. It is not a tie bus. The battery bus is connected to the HBB by a contactor.

The a/c is fitted with a Common Return Network. Big bonding leads and metal busses that run along the fuselage and wings. I understand it weighs about 400 lb.
Each electrical device is connected to it for earth return.


The big loads such as Air con compressors are fed from variable frequency electronic controllers. +/-270vdc.




Posted from Pprune.org App for Android

[EEngr]

kenneth house (http://www.pprune.org/members/407907-kenneth-house)

Since it is brushless and synchronous, i.e. frequency varies with speed, it would seem to be a permanent magnet rotor machine, with 3-phase wye winding plus neutral for the stator.Not really. Here is a diagram of a CSD and generator:

http://www.pprune.org/tech-log/477436-what-exactly-generator-field-also-744-iru-battery-wheel-well-warning-horn.html#post7027969

Ignore the mechanical stuff and look at the schematic. Inside the generator, the field winding is supplied by an exciter generator. Essentially a little three phase generator on the same shaft, turned inside-out. Its output windings are on the rotor and rectified to supply the DC to the main generator field.

The main field is controlled (indirectly) by varying the exciter field (mounted on the generator case). The end effect is to have a controllable field with no brushes (high maintenance items).

Some generators do have a PMG (permanent magnet generator) in addition to all of the above. But this feeds control circuitry in the GCU enabling the system to 'black start' once the prime mover (turbine) is spinning. But since the 787 cannot start engines without some source of electrical power, the PMG function is less critical. I'm not sure if it has one.
:8

[Ian W]

FlightPathOBN (http://www.pprune.org/members/351467-flightpathobn)

The test flight is a 'nominal' baseline exercise.

The FAA has egg all over its face from its original certification, they will be ensuring with their new brought in experts that everything is checked out and double checked and that all recommended certification tests are totally and painstakingly carried out with all results as expected.

Boeing also with its new brought in experts MUST ensure not only that the aircraft passes these re-certification tests but also that there is no other battery problem in the next several years - or the company would be in a company threatening situation.

I am surprised at the number of people commenting that do not realize that for both FAA and Boeing it is essential that this testing is thorough and completely correctly carried out to the latest standards. There will be no skimping, clever dodges or short cuts for this certification testing, as one or the other or both of FAA and Boeing would really have problems if the aircraft are re-released to fly and another battery issue is found.

[kenneth house]

@EEngr Thank you for posting the link to the CSD and generator schematics, that is a really clever design to avoid using brushes and magnets for an alternator. Do you also have a schematic for the starter portion--does it use some separate windings to become a motor?

[kenneth house]

@ TURIN:
Are there any battery packs or capacitors to store or hold up the 270 buss, or is it just created as needed?

[TURIN]

Kenneth.
No there aren't.

The Common Motor Starter Controllers (CMSC) alter the frequency of the +/-270VDC as required to control the speed & torque of the various big motors such as engine starters, air con compressors etc.
Creates a lot of heat which is why they are liquid cooled.
Much of this is covered in the early posts of this and other 787 threads.



Posted from Pprune.org App for Android

[FlightPathOBN]

What are you guys talking about, it has been fixed! :mad:

United Airlines puts 787s in schedule for May 31 (http://www.king5.com/news/aerospace/United-Airlines-puts-787-schedule-201998721.html)

[FlightPathOBN]

The NTSB hearing on the batteries is taking place right now...very, very interesting...

National Transportation Safety Board (http://www.capitolconnection.net/capcon/ntsb/live/ntsblive_flv.htm)

(and damn, the NTSB chair is a very striking woman!)

in the morning, there was some very revealing data..

Foremost, in my mind, was that with the relative small number of large batteries produced (like on the 787) that there is not enough data to support the 10 minus 6 failure rate protection. The large batteries are produced in small batches, which there just isnt enough data yet to form a solid failure rate. The panel speaker from NASA noted a 3% initial rejection rate on the batteries they get, which is far above 1/10MM.

The battery electrolyte being flammable, not combustible, was a big issue for many on the NTSB Board

Another issue for the 787 battery was the size/shape, several panel speakers noted the large shape, with expansion/contraction from charge/discharge was an issue, and that the rectangular shape, in expansion/contraction, can cause issues. The panel speaker noted that this can cause failures, ie internal shorts, that are not picked up during the initial manufacturers testing of the battery prior to ship.

[FlightPathOBN]

Hopefully, everyone is watching this....


it is F'n amazing.

from the automated CC of the meeting:

>> WE LOOK AT THAT STATISTICALLY. TYPICALLY THERE HAS BEEN A VERY GOOD SAFETY RECORD FOR LITHIUM BATTERIES OVER THE YEARS. BUT WE ALWAYS HAVE TO LOOK AT THE RISK WHAT IF SOMETHING DID GO WRONG. WHAT IF THERE WAS A FIRE UNRELATED TO THE BATTERY? IT DOES NOT MEAN THEY ARE NOT SAFE BUT THEY ARE PRESENT. IF THERE WAS AN UNRELATED FIRE AND THEY BECAME INVOLVED, WOULD THAT CHANGE ANYTHING? WOULD THAT BE SOMETHING WE SHOULD LOOK AT?

>> HAS DOT DONE ANY EVALUATIONS OF HOW MANY AIRCRAFT WE COULD LOOSE? DUE TO THIS RISK?

>> THERE IS A RISK ANALYSIS ON THE FAA TECH CENTER WEBSITE. JUST RECENTLY BEEN UPDATED. AN UPDATED VERSION WILL BE AVAILABLE NEXT WEEK. THERE IS ANALYSIS ON THE WEBSITE THAT THEY COMMISSIONED IN TRYING TO ASSESS DIFFERENT MITIGATION STRATEGIES IN DIFFERENT TYPES OF AIRCRAFT, A DIFFERENT WAY OF VIEWING AT TRYING TO PROVIDE MITIGATION WITHOUT A COMPLETE RETROFIT OF FREIGHTERS.

>> DO THEY ESTIMATE THE NUMBER OF AIRCRAFT THEY THINK COULD BE LOST?

>> THEY DO. THE ESTIMATE IS APPROXIMATELY ONE EVERY TWO YEARS.

This is the direction it is going

Chair of NTSB...

ONE OF THE THINGS I WAS STRUCK BY FROM ALL OF THE PANELISTS THIS MORNING AS THERE IS A LITTLE BIT OF A CHICKEN AND EGG PROBLEM WITH THE STANDARD. IT SEEMS LIKE YOU HAVE TO HAVE ENOUGH DEVELOPMENT TO GET TO A POINT TO SAY WE NEED A STANDARD. EARLY ON THERE IS SO MUCH PROPRIETARY INTEREST THERE IS PROBABLY NOT GOING TO BE A LOT OF SHARING ABOUT THE TECHNOLOGY AND STRATEGIES. HOW DO YOU KNOW THAT IS THE RIGHT TIME TO CONVENE TO DO STANDARDS AND ALSO THAT YOU ACTUALLY END UP HAVING PEOPLE BUT ARE NOT SO COMMITTED TO THEIR OWN TECHNOLOGY THAT THEY DRIVE THE STANDARD? I UNDERSTAND YOU HAVE TO HAVE A LOT OF PARTICIPANTS. I THINK IT GETS COMPLICATED.

one very interesting question:

She asked if the batteries from the 787 would be allowed to be carried as cargo.

The FAA answered that yes in the US, as Class 9 HAZ, (but they had a modification to standards to allow it) and no according to ICAO.

Chair:

THE FINAL QUESTION IS PERFORMANCE STANDARDS. THAT IS WHAT WE NEED. WHAT HAPPENS WHEN THE STANDARDS DO NOT BEAR OUT IN THE REAL WORLD OF EXPERIENCE? WHERE IS THE SAFETY VALVE THEN? YOU HAVE CREATED A SET OF EXPECTATIONS PEOPLE ARE SUPPOSED TO PERFORM TWO. IF THAT DOES NOT BEAR OUT, WHAT IS NEXT?

[FlightPathOBN]

Wrap up question and answers to the testing and cert standards panels (FAA, SAE, UL)

>> ONE QUICK QUESTION , I WANT AN INDUSTRY PERSPECTIVE, STANDARDS PERSPECTIVE. THAT MEANS YOU GET TO DO THIS ON YOUR OWN AND YOU THREE WORK TOGETHER. I'M TRYING TO GIVE YOU TIME. IF YOU COULD HAVE THE BIGGEST SAFETY CHANGE TOMORROW THAT WOULD MAKE A DIFFERENCE, WHAT WOULD THAT BE? NOBODY TYPICALLY COMES AND SAYS WE NEED MORE REGULATION. INSTEAD, YOU HAVE TALKED ABOUT HARMONIZATION, AND NONCOMPLIANCE, REACTION TO THE INNOVATION, I AM CURIOUS, INDUSTRY, REGULATORY AND STANDARDS, WHAT WOULD BE THE BIGGEST THING TO MAKE A DIFFERENCE? PARDON ME? [INDISCERNIBLE] [LAUGHTER] NICE TRY. THEY HAVE TO TALK AND COME TO AN AGREEMENT.

>> IS THREE AND THREE AGAINST ONE. I WOULD HAVE TO SAY -- AGAIN, THE LACK OF HARMONY IN THE U.S. HAS BEEN DIFFICULT. IF I HAD MY WISH, I WOULD WISH THEY WOULD PUBLISH A FINAL RULE TOMORROW. THE ICAO DANGEROUS GOODS PANEL DID A FANTASTIC JOB NAVIGATING WHAT IS A VERY COMPLEX ISSUE. THAT WOULD BE THE NUMBER ONE THING. AN IMMEDIATE RULE TO HARMONIZE.

>> GREAT. ONE SENTENCE OR LESS. FROM A REGULATORY PERSPECTIVE. WHAT WOULD YOU WANT TO CHANGE?

>> DEVELOP AND INHERENTLY SAFE BATTERY.

>> INTERESTING. -- DEVELOP AN INHERENTLY SAFE BATTERY.

>> INTERESTING. FASCINATING. GREAT. THE THIRD ONE.

>> A TEST METHOD TO ASSESS THE RESILIENCE TO THERMAL PROPAGATION OF A BATTERY SYSTEM.

>> THOSE ARE THREE GREAT ONES. THANK YOU VERY MUCH.

[s e t h]

jees if one takes a negative stance to the responder one could read:
DEVELOP AND INHERENTLY SAFE BATTERY. (these lithiums are inherently unsafe)
A TEST METHOD TO ASSESS THE RESILIENCE TO THERMAL PROPAGATION OF A BATTERY SYSTEM (we have no idea what will happen if a cell explodes/ignites)
THEY DO. THE ESTIMATE IS APPROXIMATELY ONE EVERY TWO YEARS (the faa expects an aircraft every two years to be lost due to the risks of external fires setting the batteries off)

and lets not forget someone put the first design in the air the first place

i have to say i like the idea posted earlier about using the 787 for freight only for some time till they have seen how well the various fixes have stopped the fires

if they had so many problems initially it should be easy to see what differences exist due to the new design

i may be being a party pooper but with a bucketload of innocent lives on the line a little more caution than has been displayed recently seems to be not too much to ask

[Machaca]

Before glibly commenting, I recommend studying today's presentations at the NTSB's Forum on Lithium Ion Batteries in Transportation:


Panel One

Introduction to Batteries and Li-Ion Cells (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Whittingham%20Presentation%20-%20Battery%20Forum.pdf) - M. Stanley Whittingham, M. A., D. Phil, Binghamton University

Advances in Lithium Ion Technology and Applications (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Chiang%20Presentation%20-%20Battery%20Forum.pdf) - Yet-Ming Chiang, Department of Materials Science and Engineering, Massachusetts Institute of Technology

Saft's Approach to High Quality Lithium Ion Products (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Bowling%20Saft%20Presentation%20-%20Battery%20Forum.pdf) - Glen Bowling, Saft Specialty Battery Group

Failure Mechanisms of Li-ion Batteries (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Doughty%20Sandia%20Presentation%20-%20Battery%20Forum.pdf) - Daniel H. Doughty, Ph.D., Battery Safety Consulting Inc.

End User Acceptance: Requirements or Specifications, Certification, & Testing (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Jeevarajan%20NASA%20presentation%20-%20Battery%20Forum.pdf) - Judith Jeevarajan, Ph.D., Power Systems Branch, NASA-Johnson Space Center, Engineering Directorate

Recent High Profile Safety Events In Lithium-ion (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Visco%20Quallion%20Presentation%20-%20Battery%20Forum.pdf) - Vincent Visco, Quallion LLC


Panel Two

UN Lithium Battery Transport, Tests & UL Battery Safety Standards (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Florence%20UL%20Presentation%20-%20Battery%20Forum.pdf) - Status Update - Laurie Florence, UL LLC

RTCA Background on Standards for Lithium Batteries (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Jenny%20RTCA%20Presentation%20-%20Battery%20Forum.pdf) - Margaret Jenny, RTCA

Regulations and Standards (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Kerchner%20PRBA%20Presentation%20-%20Battery%20Forum.pdf) - George A. Kerchner, PRBA – The Rechargeable Battery Association

Air Safety Cargo Transport initiatives (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/McLaughlin%20FAA%20Presentation%20-%20Battery%20Forum.pdf) - Janet McLaughlin, Federal Aviation Administration

Automotive Industry Standards for the Safe Use of Lithium-Ion Battery Packs (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Wilson%20SAE%20Presentation%20-%20Battery%20Forum.pdf) - Keith Wilson, SAE International

Lithium-Ion Battery Regulations (http://www.ntsb.gov/news/events/2013/batteryforum/presentations/Pfund-Leary%20PHMSA%20Presentation%20-%20Battery%20Forum.pdf) - Duane Pfund and Kevin Leary, Pipeline and Hazardous Materials Safety Administration

[FlightPathOBN]

Thanks for the link machaca...do you know if the transcript will be available?

[inetdog]

FlightPathOBN:
Even though the live feed is over, the caption window at that link will allow you to copy and paste the entire 713 line auto-caption content, beginning to end. Not nearly as friendly as a proper transcript, but still better than nothing.

[FlightPathOBN]

inet,

thanks...I would certainly point others to look at this, the content, and the intent.

[Machaca]

...do you know if the transcript will be available?


It is my understanding both transcripts and videos of all the sessions will be available next week on the NTSB website.

[john_tullamarine]

Thread Part 2 starts here (http://www.pprune.org/tech-log/512398-787-batteries-chargers-part-2-a.html#post7789492)