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The investigation is ongoing

The National Transportation Safety Board announced over the weekend that x-rays and CT scans of the lithium-ion battery pack that caught fire in a Boeing 787 Dreamliner in Boston recently was not overcharged. The battery in question powered the plane’s auxiliary power unit and the investigators have disassembled the battery and are still investigating some of the individual battery cells.

The battery fire has led airlines to stop flying the 787 planes around the world. The NTSB investigators have also said that they have examined several other components from the aircraft including battery management circuit boards and associated bundles of wire. The investigators also intend to continue testing components such as the battery charger and battery management unit.

The investigators have announced that the plane's flight data recorder indicates that the battery never exceeded its design voltage of 32 volts. The FAA issued a directive last week that the Boeing 787 Dreamliner should not fly until any problems with the battery packs are resolved.
Boeing has announced that it will halt deliveries of the 787 to customers while it works with the FAA to solve the battery issues. The batteries at the center of the investigation are lithium-ion units manufactured in Japan by GS Yusana under a subcontract to a company called Thales.

Source: CNN

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Just a guess
By EyesWideOpen on 1/21/2013 12:53:17 PM , Rating: 1
Aircraft systems are exposed to a lot of vibration and the batteries are probably shorting out due to the effects of vibration.

RE: Just a guess
By Samus on 1/21/2013 1:29:02 PM , Rating: 2
I agree. And not just vibration, but pressure and temperature extremes, all of which are not well tolerated by lithium (ion) cells. Lithium Polymer would be better suited but I'm sure Boeing chose Li-ion because of its more 'mature' industrial status.

All I can say: my Milwaukee 18v lithium drill battery only took a few drops before shorting out and failing, whereas my R/C Truck LiPo pack has taken impacts so harsh it has been ejected from the vehicle into a concrete wall, and it continues to function fine.

RE: Just a guess
By nafhan on 1/21/2013 2:15:51 PM , Rating: 1
not just vibration, but pressure and temperature extremes, all of which are not well tolerated by lithium (ion) cells
While that makes sense, one would assume that Boeing did a bunch of testing that exposed the batteries and the entire aircraft to those conditions - repeatedly. I'm very interested in hearing how they missed this problem in their testing.

RE: Just a guess
By Keeir on 1/21/2013 2:44:57 PM , Rating: 4
but I'm sure Boeing chose Li-ion because of its more 'mature' industrial status.

Battery choice was made in 2005-2006 timeframe and a contract was awarded. This was a multi-level contract in that Boeing (US) contracted Thales (France) who contracted Yusua (Japan).

This was before the Sony issue. At the time the initial choice was made, there was little conrete real world evidence that Lithium Cobalt Ion batteries were a potential problem. Once the contract is awarded, changing the details of the contract mean serious money. Without a "proven" safety risk, Boeing (management) wouldn't force Thales to change it's supplier.

RE: Just a guess
By Justin Time on 1/21/2013 5:26:06 PM , Rating: 2
Boeing would be well aware of this, and would have tested for just such conditions. Far more likely to be a mfg fault than an untested operating environment.

IEEE's theory
By gamerk2 on 1/21/2013 2:51:23 PM , Rating: 3

It seems that the batteries heated up in a self-accelerating pattern called thermal runaway. Heat from the production of electricity speeds up the production of electricity, and… you’re off. This sort of things happens in a variety of reactions, not just in batteries, let alone the Li-ion kind. But thermal runaway is particularly grave in Li-ion batteries because they pack a lot more power than the tried-and-true metal-hydride ones, not to speak of Ye Olde lead-acid.

So the IEEE is theorizing that thermals could be to blame. Makes more sense then most theories here.

RE: IEEE's theory
By drycrust3 on 1/22/2013 10:38:02 AM , Rating: 2
The problem with the thermal theory is the cells at the end of the battery box seem to be the ones that have collapsed, which suggests they were the ones that actually failed, not the ones in the middle, which is where it would be hardest to dissipate heat.

RE: IEEE's theory
By puplan on 1/22/2013 3:05:11 PM , Rating: 2
Not necessarily. It depends on battery surrounding (airflow, contact with heat dissipating surfaces, etc.).

More details
By bug77 on 1/21/2013 12:54:18 PM , Rating: 3
Here's an informed discussion about the subject:

RE: More details
By Sivar on 2/5/2013 12:15:07 PM , Rating: 2
Informed discussion?

You must be new around here.

oversimplication, I hope
By DockScience on 1/21/2013 1:17:48 PM , Rating: 2
I hope this is an oversimplication by the NTSB for the press.

A battery voltage means NOTHING in a lithium battery.

It's the individual 3.7v cell voltages that count.
A single cell can overcharge, go thermal runaway and start a chain reaction with perfectly wonderful cells.

battery charging
By ssobol on 1/21/2013 4:41:40 PM , Rating: 2
The charging current is much more important than the voltage when dealing with these types of batteries. The lower the charge current, the less likely that the battery will fail. However, Boeing must balance the charge current versus the recharge time.

The vibration environment in a modern airliner is probably less than in most other vehicles. I would say that the vibration environment of the Chevy Volt battery is worse.

But due to the energy stored in lithium batteries, a failure of one cell would certainly lead to a failure of the entire battery in short order. Perhaps the 787 needs to have the battery cells in separate cases to limit the damage if one fails.

By wavetrex on 1/21/2013 4:52:40 PM , Rating: 2
Why Li-Ion?

LiFePO4 (Lithium iron phosphate) batteries are used successfully in a LOT of electric vehicles around the world without any problem.

They last longer, they are more resistant and do not get fire when overcharged.

(Think A123 batteries)

But they are a more modern technology and because of stupid bureaucracy, Boeing didn't update the battery system after the plane was initially designed some 20 years ago.

Missing Battery Metrics
By toyotabedzrock on 1/21/2013 5:03:09 PM , Rating: 2
The more important metric for monitoring a lipo during charging is the amperage. And it must be monitored cell by cell. I hope they have that data in the blackbox.

Also want to point out that these are double outsourced batteries. Maybe the Japanese company outsourced to China, they make horrible batteries.

By maugrimtr on 1/23/2013 10:40:39 AM , Rating: 2
The National Transportation Safety Board announced over the weekend that x-rays and CT scans of the lithium-ion battery pack that caught fire in a Boeing 787 Dreamliner in Boston recently was not overcharged.

Sometimes, DT's descent into being incapable of using a spellcheck can be humorous.

By JimboK29 on 1/21/13, Rating: -1
RE: GM/Boeing
By lennylim on 1/21/2013 1:47:20 PM , Rating: 2
Actually, more like Fisker Karma, isn't it?

RE: GM/Boeing
By RDO CA on 1/21/2013 4:01:52 PM , Rating: 2
You might think you are funny but not to look like a dumb a$$ you might do the research to what happened to the Volt first and not just listen to others that are as clueless on the issue.

"What would I do? I'd shut it down and give the money back to the shareholders." -- Michael Dell, after being asked what to do with Apple Computer in 1997
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