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Investigation continues focusing on battery certification

The investigation into the fire that affected a Japanese Airlines Boeing 787 Dreamliner at Boston Logan Airport on January 7 has pinpointed the source of the fire. According to the NTSB, the JAL lithium-ion battery comprised of eight individual cells showed multiple signs of short-circuiting leading to a thermal runaway condition.

That thermal runaway condition then cascaded to other cells in the battery leading to the blaze. According to the NTSB, charred battery components indicated that the temperature inside the battery case exceeded 500°F. The focus of the investigation moving forward will now be on the design and certification requirements for the battery system.

"U.S. airlines carry about two million people through the skies safely every day, which has been achieved in large part through design redundancy and layers of defense," said Hersman. "Our task now is to see if enough - and appropriate - layers of defense and adequate checks were built into the design, certification and manufacturing of this battery."

Boeing 787 production line [Image Source: Boeing]

The investigation has ruled out mechanical impact damage to the battery and external short-circuiting. There were signs of deformation and electrical arcing on the battery case not related to the cause of the fire according to investigators. Boeing had tested the battery during the 787 certification process and found no evidence to support that this sort of fire within the battery pack could occur.

Boeing has issued a statement on the investigation update stating that it plans to remain committed to working with the NTSB and the FAA along with its customers to maintain a high level of safety. “The 787 was certified following a rigorous Boeing test program and an extensive certification program conducted by the FAA. We provided testing and analysis in support of the requirements of the FAA special conditions associated with the use of lithium ion batteries,” said Boeing’s Marc Birtel. “We are working collaboratively to address questions about our testing and compliance with certification standards, and we will not hesitate to make changes that lead to improved testing processes and products.”

Sources: Boeing, NTSB

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By michael67 on 2/11/2013 2:06:01 PM , Rating: 2
Actually i don't get why they use big batteries, as the problem of a thermal runaway is long know.

Friend of a friend of mine rebuild a Ford Capri Mk III to total EV, and mainly to do dragster races with it, as EV gives almost 100% torque over the hole range of RPM.

And instead if using big cells, he uses small cells in a parallel/serial setup, and he also use liquid cooling to prevent a thermal runaway, as he draws maximum power from the cells, and they get hot then.

Power cells:
Electronic Cool Liquid:

He uses a big pump and a car radiator to cool the cells.

He dose not of course install not a cooling system with the extra consumption of the pump, and add the extra weight of the cooling Liquid and waterproof housing, if that was not necessary.

The use of small cells had two major advantages for him, and three for airplanes.

* A small cell is much easier to cool.
* Replacement of a single cell was much cheaper, since not all cells simultaneously break or age at the same time/speed.
* Extra redundancy by using parallel cells.

A well engineered cooling system dose not have to add a lot of extra weight, as a double wall plastic shell for the cell's with a gap of 1~2mm for liquid is enough to keep the cells cool.

If a serious hobyist already knows he should stay away from large cells in relation to fire, it is outrageous that a team of highly paid engineers at Boeing don't know that aider. 0_o

"We don't know how to make a $500 computer that's not a piece of junk." -- Apple CEO Steve Jobs
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