Japan probe finds 787 battery not overcharged

By ELAINE KURTENBACH

National Jan. 24, 2013 - 06:47AM JST ( 11 )

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11 Comments

-8

basroilJan. 24, 2013 - 11:50AM JST

Goto said the maximum voltage recorded for the battery was 31 volts, which was below its 32 volt limit. But the data also showed a sudden, unexplained drop in the battery’s voltage, he said

There we go, all that fuss to say that the battery shorted out. Now rather than 90% chance of manufacturing error, it's 95%. Next bit of information will be that a machine at Yuasa's electrolyte factory was "abnormally worn down" and that the two batteries were from the same lot.
1

KnowBetterJan. 24, 2013 - 01:15PM JST

Hmmm, the battery 'connected to the aircraft's wiring' showed a sudden voltage drop. In the electrical engineering world we would say that battery's load either suddenly surged or shorted. Either way that is how a battery 'suddenly shows a drop in voltage'. They quote "the data also showed a sudden, unexplained drop in the battery’s voltage" were 'unexplained' simply means we have not looked into what caused that or have not gotten that far into the investigation. Sure they have but they are not ready yet to lay blame until everyone is on board with how they are going to downplay the cause which is NOT the batteries but wiring and/or circuit failure(s) which would hurt far more people working on the Dreamliner than simply blaming it on a simply little battery using 20 year old technology. Come on people are you that simple that you'd think the battery is the problem. I see the tail already starting to wag the dog but if it restores the public's confidence in the 787 and Boeing gets back to work churning out more flawed aircraft then what's they worry?
-5

basroilJan. 24, 2013 - 02:36PM JST

KnowBetterJan. 24, 2013 - 01:15PM JST

In the electrical engineering world we would say that battery's load either suddenly surged or shorted.

In the hobby batteries world, we would say "damn battery shorted out, better get it out of the garage before it vents". Li-ion batteries can have internal shorts that are caused by manufacturing errors, resulting in uncontrolled internal discharge (and sudden battery voltage drops)
0

gonemadJan. 24, 2013 - 08:30PM JST

In the electrical engineering world we would say that battery's load either suddenly surged or shorted.

The battery should have protection circuits for this case. Therefore I tend to agree with basroil that this an indication of a manufacturing flaw of the battery.

What I wonder though is at what time differences the battery voltage is sampled and whether the monitoring circuit on the plane is really capable of detecting small glitches which might damage the battery electronics.
1

ebisenJan. 24, 2013 - 08:40PM JST

basroil, you do sound like someone who had absolutely no idea about how LiIon batteries are being made and work

a sudden drop in voltage followed by smoke and fire could mean that a cell reached L6 on the failure scale, and that the failure propagated to the neighbouring cells. This means nothing with respect to the manufacture quality, yet, as we don't know what caused this failure.

could be a too high C rate ( o r charging or discharging current). Could be a too high peak power current, together with already a hot cell. In any case, the chances that a cell from Yuasa fails spontaneously like this are incredibly small... never mind two accidents happening in the same week.

consider that such a fire could easily be initiated by failing electronics igniting and heating up neighbouring cells

therefore still Thales S.A. has the responsibility of putting a package together that works properly and ensure the cells are not overloaded.
-1

warnerbroJan. 24, 2013 - 09:09PM JST

Why don't they stop pretending to investigate and leave it to the Americans? As long as a Japanese company is involved we'll be unlikely to see the truth from Japanese bureaucrats.
-6

basroilJan. 24, 2013 - 10:45PM JST

ebisenJan. 24, 2013 - 08:40PM JST

sound like someone who had absolutely no idea about how LiIon batteries are being made and work

could be a too high C rate ( o r charging or discharging current). Could be a too high peak power current

Says the guy who doesn't realize that a "C rating" is the discharge current rating, and is often expressed as "sustained C/ burst C", and is calculated as a multiple of the Ah rating of the battery. A high C rating (C is a rate by itself, expressed in amperes, which is current flux) is a good thing to prevent overheating, though means you can easily output too much power for other circuits to handle. Interestingly, it doesn't matter how big a battery is, at a certain C rating for charge it will charge in the same time.

They already ruled out over-voltage, overcharging, and over-current (during charging, at least in the Boston one), the three things that the Japanese investigators were looking for. But you know what? Those three things are all attempts to put the blame on someone other than Yuasa! http://news.in.msn.com/business/defective-batteries-may-be-cause-behind-dreamliners-grounding If you look carefully, what I've been saying all along is right there, these batteries are replacement ones installed recently, which makes a bad batch the single highest probability cause.
0

ebisenJan. 25, 2013 - 08:21AM JST

basroil

I don't want to lecture you but:

Says the guy who doesn't realize that a "C rating" is the discharge current rating

Not only discharge but also charge. For your information a 10Ah cell charged at 1C means that it will be charged in 1 hour from 0 to 100%SOC (state of charge). Thant's why:

C is a rate by itself, expressed in amperes, which is current flux

make no sense. C has no unit (definitely not expressed in Amperes) and amperes express a current. BTW in case of electricity we don't use the term current flux, due to the conduction on the wire's external surface only. Only a current. More:

Interestingly, it doesn't matter how big a battery is, at a certain C rating for charge it will charge in the same time.

Not interesting at all, the C rating is a convention. Any cell, charged at 2C will charge in 30 minutes, charged at 0.5C will charge in 2 hours. For example in case of our 10Ah cell, 2C means 20Ampers current -> charged in 30 minutes, 0.5C means 5Ampers, and so one. OK?

What I tried to say in my previous e-mail is that the failure can't be spontaneous, even the cheapest Chinese cells will withstand being used normally for 2 years without bursting into flames right now. Never mind that Yuasa is THE PLACE TO GO when one needs the best of the best (satellite and space applications).

Therefore the chance that TWO of these accidents happen unprovoked, with two normally used Yuasa cells, in such a short time-span are incredibly low. That's why I believe that this is not a failure of the Li-Ion technology, but of the electronic controllers, not keeping the cells within the specified safe parameters.
-5

basroilJan. 25, 2013 - 10:45AM JST

ebisenJan. 25, 2013 - 08:21AM JST

two normally used Yuasa cells, in such a short time-span are incredibly low.

Yuasa has never sold the LVP cells for any application other than the 787. They have other cells used in other industries, but this is their first and only aircraft cell.

And should have been "charge flux", because current is flux.
0

ebisenJan. 25, 2013 - 03:41PM JST

Basroil: let me Google it for you... Yeah - here we go:

http://www.gsyuasa-lp.com/gylp-markets

Their aerospace work is mostly classified, but yes, you can document yourself there. From their page:

The power systems of more than 50 satellites have relied on GS Yuasa’s Li-ion cell technology for a total of more than 1,100,000Wh on orbit (over 37 million working cell hours) without anomaly or failure. On a total energy storage capacity basis (Wh), GS Yuasa is a world leader in Li-ion for space.

Not so easy to kick at them now, isn't it.

PS - the International Space Station will also be powered by GS Yuasa cells, on a new contract from P&W.
-4

basroilJan. 25, 2013 - 04:57PM JST

ebisenJan. 25, 2013 - 03:41PM JST

let me Google it for you... Yeah - here we go:

http://www.gsyuasa-lp.com/gylp-markets

You need to learn to use google....

http://www.gsyuasa-lp.com/aviation-lithium-ion-markets

And I quote: "GS Yuasa’s lithium ion cells were chosen for the Electrical Power Conversion System in Boeing’s next generation commercial airliner, the 787 Dreamliner. This contract is a historic first as it marks the first commercial aviation application of Li-ion technology anywhere in the world."

Or in more simple statements, these cells (not that I never mentioned anything about OTHER cells, only the LVP line) have never been used in aviation. You can go off topic all you want, but the fact is that these cells are their first mass produced cells for critical operations, and first aviation cells period.

And for your information, 1 million Wh cycled charge is kind of pathetic, only about as much as two dozen laptops will see in their lifetimes. I don't know how you can consider a million Wh to be amazing considering there's a million times more power used a year without anomalies in cellphones and laptops alone. The last major Li-ion battery recall involved tens of millions of cells that had seen perhaps a few billion Wh.