the Cynic in me hopes this is just a simple imperial to metric error.. eg batts sending temp out in celsius but the charger is expecting fahrenheit.

FYI The Seattle Times illustration claims the batteries have lithium cobalt oxide cathodes. This is what I thought initially as well, as it was the original spec for test/certification aircraft.

However it seems production aircraft may have been fitted with (more safe) lithium manganese oxide batteries, according to Turins anf Fargoos B787 training notes, and an article from 2008.

The sealed lead batteries on the B777 (particularly the main battery that seemed to have a higher failure rate) can go into thermal runaway and start smoking.

ScareBatt
 

Machinbird:

Quote:

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As a betting man, I'll bet that the issue with the battery is actually with the charging system and insufficient feedback from the battery to the charging system regarding cell temperature. The charging system should not continue to charge a battery that is moving in the direction of thermal runaway.

---

The closed loop System must use TEMPERATURE and VOLTAGE. Before thermal runaway the cell voltage becomes abnormal. Just a cell is actually critical. When arranging in series or series-parallel the issue becomes complex. And dangerous.

ScareBatt :mad:

My pilot son before the RTW flight made a lot of dangerous uses of LiPo in the RC models. :E Extra precautions were made here. We simulated how to proceed, just in case after youtube watching. :E

Number of cells
 

Diamond Bob:

Quote:

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Looks like the battery had 8 cells, according to this graphic accompanying a story in the Seattle Times. In another forum someone who seemed to know says that both the APU start battery and the main battery are the same unit.

---

Thanks bob, this points to another issue. They designed a non conventional circuitry (charger, ETC.) to manage the higher voltage (29,6 V nominal up to 33,6 V "floating" voltage). Aviation uses 24 ~28 V span. A battery replacement would require a redesign, etc. (time consuming) of critical circuitry. :{

I hope for charger issues. (best case scenario)

Batteries are "female". Some surprises are trouble.
 

Ngineer:

Quote:

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The sealed lead batteries on the B777 (particularly the main battery that seemed to have a higher failure rate) can go into thermal runaway and start smoking.

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For sure! (bold mine)

Batteries are not a simple issue. I had problems with ALL types in my professional life. I remember in first year of academy i read a russian book on batteries. I was amazed how complex were. (1970). Today we need microprocessors to manage them. :mad:

While ANA was quoted on Wednesday saying they expected to by flying again within a few days, it seems they have now changed their mind. Until the wee hours of Friday morning (Japanese time), this is what their reservation change policy read:

"2. Waiver of Date change and Cancellation
Application period until January 23rd, 2013
(1) Date change
One time date change is possible without regardless of the fare rule. The date change is subject to space availability and the new departure date must be until March 31st, 2013. (including arriving Japan on April 1st,2013)
(2) Waiver of Cancellation and Refund charge
Cancellation charges or refund charges will be waived irrespective of the fare rules.
"

The application period has now been extended to March 31st.

...
 

Please define "best". I agree with "beautiful". We'll see about composite and "mature" ... I'm sure everybody thinks about the Comets and its nice large windows all the time ... damn shame that one. De Havilland was such a great company.

About the battery voltage, number of cells and such, Boeing might be using various power converters (DC-DC etc) between the batteries and electrical systems. It might well be more efficient to design the battery array at its optimal voltage/configuration, then convert to the optimal voltage for the electrical system. Having said that the burnt battery does look like 8 cells. But it wasn't the main battery was it?

With some of the power figures being talked about (1.4MW in one post -- can that really be right?), I'd expect conversion to high voltages for distribution. Otherwise they would be talking about the airplane being mostly copper rather than composite.



For that matter (just conjecture) it might be interesting to contemplate a "distributed" battery. Rather than co-locating many cells, place single cell (or low cell count) batteries at various places so one cell cannot heat another one. Each one can have an independent charger/controller and can convert its 4V output to 28V (or go 2 cell / 8V if 4V isn't enough headroom for the power converters).

But then maybe you'd have to duplicate the thermal protection / detection systems so perhaps inefficient.

Are there any photos of the top of the battery? The one I saw had the top missing but was it removed or ??

Edit: This looks like it might be it..

http://media.komonews.com/images/130..._battery_1.jpg

Not so. The battery voltage, under charge, sits at 33v quite often in the older "Boeing" jet I fly. ;)

That is the charging voltage being measured, not the battery voltage!

If you charge a 28V battery at 28V you will still be waiting for it to be charged next Xmas! ;-)

Jp Authorities release ANA 787 battery photos
 

See them here in the Yomiuri.
‚V‚W‚VƒoƒbƒeƒŠ�[‰æ‘œŒö•\�A—eŠí“à‘S‘Ì‚ª’Y‰» : ŽÐ‰ï : YOMIURI ONLINE�i“Ç”„�V•·�j

I know that is supposed to be a joke but in fact they may eventually burn.

'Charging' at this rate will eventually lead the battery to become completely discharged where we get into another 'danger area' for the Lithium based high energy density system.

Too much charge =risk of thermal runaway.
Too little charge =risk of thermal runaway.
Too high temperature =risk of thermal runaway.
Cell short circuit. =risk of thermal runaway.
Loss of charging voltage regulation =risk of thermal runaway.
Excessive AC ripple =risk of thermal runaway.

To use these batteries in a safety critical situation they not only need to pass strict quality control and be installed correctly, but also require a reasonably complex system of monitoring voltages and temperatures to control charging.

If all this works as it should, then there is no reason for any Li-Ion battery to get anywhere near thermal runaway. Redundancy in this system is the way to go rather than ensuring enough distilled water is available to douse the fire when it does happen.

Boeing will be hoping that the two batteries involved turn out to be from a faulty batch at Yuasa. Redesigning an inherently inadequate charging system is likely to take some time. :-(

NiCd´s?
 

Capn Bloggs:

Quote:

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The battery voltage, under charge, sits at 33v quite often in the older "Boeing" jet I fly.

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Could you check the number of cells (series) in this case?

You can (reducing batt life) keep them more charged. Until a certain point. Excessive gassing (lead acid) or higher temperature (NiCd). Both are NOT CRITICAL like the Lithium counterparts.

In lithium ones you need to monitor carefully temperature and even ea. cell voltage (early warning on impending problems)

Float current is what you need to keep an eye on with these 'systems'.

SoS

Hope not a dumb question. I was trained, in utilizing this type of battery, to isolate a cell from concurrent charge/discharge. The system prevented a battery from being used whilst charging. Is that what you mean by "Float"?

thanks

I wonder if the fault lies with the airlines (Only ANA/JAL aircraft involved) training and maintenance procedures OR with Boeing who may have rushed to deliver aircraft because of previous delays?
Whatever thank goodness we're not scrapping bodies off the tarmac - at least we know the alarm systems are working.

Lyman

I 'think' SoS is meaning the charging current would be adaptive to provide the correct optimal charging current for the batteries. Not too little - not too much :)

Would lifepo4 be a better choice
 

Just curious but does anyone have any idea why Boing have not chosen Lifepo4 batteries for their better safety. Ok the energy density is not quite as high but the better safety and longer life would surely outweigh this.

It seems possible to me that the design of the battery system is too focussed on having the new technology mimic the function of traditional batteries rather than making best use of the new technology. Traditional batteries are used to regulate the voltage on the busses. They are able to tolerate overcharging quite well. In my view best use of Lithium technology would involve having a separate voltage regulation system with the battery waiting in reserve, perhaps connected through a diode, to provide power in the event of a generation shortfall below demand. The battery only charged when monitoring deems necessary.

E S P....

Thanks, I assumed as much. It strikes me that in a very dynamic draw, supply situation, the Generation, load, and "surge" (battery) would have to be balanced in intricate fashion. At times , in load transition, the Battery is passive, merely a conductor, and the relative flow can create temporary overloads, and conversely, wide open draw. My question was meant to attempt to extrapolate a system I became used to, to the current one.

It strikes me that those two batteries are the pinch in a very large pipeline, so I would have expected there to be more than two batteries (each eight cells)...likewise ambient temps would seem to be rather important.

thanks for your response :ok:

Non conventional design with LiIon
 

Rory166:

Quote:

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Traditional batteries are used to regulate the voltage on the busses. They are able to tolerate overcharging quite well. In my view best use of Lithium technology would involve having a separate voltage regulation system with the battery waiting in reserve, perhaps connected through a diode, to provide power in the event of a generation shortfall below demand.

---

The info we have so far points to the second approach. Not the simpler(old) one.

state of the art battery? who wired this up???

Look at that wiring mess on top of the cells....why is there even wiring like that? this looks to me like it was hacked together...

http://seattletimes.com/ABPub/2013/01/18/2020162337.jpg

Floating voltage
 

Bear:

Quote:

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Is that what you mean by "Float"?

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See Float voltage

Definition: The voltage at which the battery is maintained after being fully charged to maintain that capacity by compensating for self-discharge of the battery.

wiring
 

Flight

The visible wiring is almost certainly the BMS connection. The heavy current connection between cells would most likely be by bars. I imagine the point you are making is that the BMS wiring would have been better tied to a supporting structure rather than draped over the cells where possibly warm metal might damage the insulation and cause a short. It does appear to be formed into a loom away from the terminals and busbars. One would hope the battery terminals would also have insulated covering. In general things often look more of a mess having caught fire than they did before.

State of the art battery
 

FPO:

Quote:

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Look at that wiring mess on top of the cells....why is there even wiring like that?

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http://seattletimes.com/ABPub/2013/01/18/2020162338.jpg

The answer is at your RH picture. The plastic plate melted an the harness resisted the heat.

What puzzles me about these battery events is why they happened when they happened? And why now for, apparently, the first time?

FYI, the ANA aircraft (Line number 9, first flight Jan. 9, 2011) and JAL aircraft (line number 84, first flight Dec. 7, 2012) came off the production line almost two years part. Line Number 1 first flight was Dec. 15, 2009.

My guess: If there aren't serious design problems, is that there are defectively manufactured electrical component(s) involved.

Intriguing indeed, i agree
 

airman1900:

Quote:

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What puzzles me about these battery events is why they happened when they happened? And why now for, apparently, the first time?

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Over voltage as reported can explain very well. But why? And the timing for the apparently same problem is intriguing.

:confused:

A software issue? We would need more info on the subsystems "around" the batteries.

NTSB at JAL 787 (BOS):

http://seattletimes.com/ABPub/2013/01/08/2020087644.jpg

You know someone at Boeng that pushed for these batteries is having a long talk with a chairman that just lost $50 million in stock options from this fiasco. 'So why didn't we go with Lead Acid batteries?'

'Well uh, well gee, um...'

HelderBerg (SAA 747 Combi downing in Indian Ocean)
 

"Helderberg crash IASA Lithium Fire"

Any aviation journalist who googles that will have a wealth of information on the first large aircraft downing due to Lithium Ion battery fires - so many decades ago now. Boeing stopped offering the "cargo in aft section of pax compartment" 747 Combi after that event. The Helderberg event coincided with the bulk carriage of Li Ion watch batteries that happened inreasingly - just as digital watches and pocket calculators were becoming the norm. That bulk carriage of Li ion batts in air-freight is now banned by IATA and the FAA. Not sure why a bunch of aircraft-powering Li Ion accumulators with an even higher power density is (perversely) OK, yet a properly packed container of segregated tiny watch/calculator/phone batteries is not.

However anybody who's seen the results of the Dell laptop battery fires would have no doubt that it's an issue best ducked. Thermal runaway that doesn't need oxygen and cannot be suppressed? Bad enough in an isolated cargo hold, but in an avionics compartment or an inaccessible APU location?
It's not as if you can make them jettisonable. A main load center/avionics compartment in a 787 is a slightly different proposition to most other aircraft that aren't so "electrical" in nature. It's the heart of what makes it fly, not just the aircraft avionics. Aircraft control becomes an issue.

The 787 was designed to be a nil hydraulics electrically powered beastie. .... so battery capacity and reliability was quintessential to safety. I'm wondering what dispensations and extra requirements specifications were finagled by Boeing engineers in the design approval process (via sympathetic FAA weenies). Maybe the new FAA administrator started looking into this after the fires started, discovered something and then had no choice but to order a "review". More power to his elbow.

If the Lithium Ion battery fires continue or there's an unexplained loss due to a crew having to quickly monitor off busses in a fire and smoke drill? That will be a nightmare for both Boeing and the FAA. It's got all the potential of a NASA Challenger disaster and a denial of leaky seals being a threat to the Space Shuttle.

But one thing is for certain. Boeing will not be giving up on those Li Ion batteries in the 787. There's no viable alternative with the required power density. And a timely fixing of a new aircraft that's both in service and on the assembly line? Burn that midnight oil you Boeing engineers. Whatever you come up with as a fix better be good.

Because things have progressed in the last "many decades"?

Boeing and the OEMs will have done their work and believe that they have properly tested this newer technology and that it is safe for aviation specific applications. That's progress. The watch batteries will not have had any such testing done, why would you spend a bucketload of cash for such an incidental part of a spec when you can just use sea freight?

Lithium ion batteries in aircraft will almost certainly become the norm, but the issues need sorting out first. As a new aircraft the 787 doesn't have the luxury of using tried and tested technology, if you did that you'd effectively get a 777, and as good an aircraft as that is the 787 is far better once the bugs are ironed out.

Battery Rupture Plate
 

Having now had the opportunity to view the manufacturers outline spec sheet for the Yuasa Li-Co cells I see the rupture plate is apparently in the side of the battery rather than on top as conventional. This might give the opportunity to place a vent path from this rupture plate to the outside rather than have the emitted chemicals destroy the rest of the contents of the battery case as seems to have happened in the pictures shown on this thread. Clearly the designers of the battery box were confident that the 4 battery management systems (2 in box 2 outside) would ensure that a cell never did rupture.

The requirement for maturity and Aeropspace certification may in this case have been counterproductive in that an older less safe battery chemistry is used in preference to a newer fundamentally safer chemistry.

Does anyone know the pressurisation status of the electronics compartment where the battery is housed. I am slightly mystified as to how the chemicals were vented overboard in one instance and smelled in cockpit and passenger compartment in another.

2 batteries
 

Mailinator

The two batteries are for different functions apparently. One as the APU power source and one as a backup for the electronics. So the battery backup has 4 monitoring systems but no backup for itself. Once the backup battery failed there would have been no backup in the event of a power failure. Does the dreamliner have a drop down aero generator anyone?

Hmmmm. A certainty ? Time will tell.

Well one was parked on the ground , and one was flying. In flight the air is extracted from the avionics bays and exits via the outflow valve. On the ground the air exits through openings under the fuselage.
Although there is positive airflow in flight from the cabin to the underfloor it is amazing how crew regularly smell things happening downstairs, even though the airflow is in the other direction.

From what I can read on the 'net the aft EE bay is the main Electrical distributor point as the 4 main starter/generators and 2 apu generators feed in there.

http://sitelife.aviationweek.com/ver...0d94d.Full.jpg

IF the above picture shows the RAT in it's production location then worryingly does it point to the emergency power distribution system being located in the aft EE bay as well.........all the eggs in one basket?

Airbus have a philosophy of physical separation of primary/secondary and emergency power supply systems with, naturally, a weight penalty.

787 smoke venting from E/E bays
 

As written in a previous post, the reason why it was possible to vent the smoke in cruise, but not on the ground is simple.

Venting is done by an overboard venturi, which only works during flight (it is only used in cases of failure, normal E/E cooling is accomplished using electric fans). On the ground, as in the Boston case, this type of venting cannot work, so smoke was able to enter the cabin.

Glad rag,

The RAT sits under the wings, but feeds into the main circuits in the forward E/E bay.

Yes, the RAT location does appear to be under the centre-section on production aircraft, unlike the photo that I posted earlier, showing one of the prototypes with a RAT forward of the nosewheel.

Here's a clearer photo that shows it deployed:

http://cdn-www.airliners.net/aviatio.../6/2177637.jpg

Unctuous.
Where did you get the idea that the 787 is a "nil hydraulics" aircraft. The only system that is electric instead of the usual hydraulic is the brakes.
Flt ctls, l/gear ops are still hydraulic.
The engines still have directly driven hydraulic pumps on the gear boxes.