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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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propagation of fire to adjacent cells??
By othercents on 2/11/2013 10:17:41 AM , Rating: 3
quote:
The NTSB learned that as part of the risk assessment Boeing conducted during the certification process, it determined that the likelihood of a smoke emission event from a 787 battery would occur less than once in every 10 million flight hours. Noting that there have been two critical battery events on the 787 fleet with fewer than 100,000 flight hours, Hersman said that "the failure rate was higher than predicted as part of the certification process and the possibility that a short circuit in a single cell could propagate to adjacent cells and result in smoke and fire must be reconsidered."


Crazy how one person can tell them that they should consider this but discounted their expertise and now they find out that it is possible to cause circuit propagation.




RE: propagation of fire to adjacent cells??
By marvdmartian on 2/11/2013 10:29:56 AM , Rating: 2
Like Bill Cosby has said (paraphrased), don't ever tempt God by using the word "can't"!!

"This CAN'T happen!!" mmm-hmmm....


RE: propagation of fire to adjacent cells??
By gamerk2 on 2/11/2013 11:25:33 AM , Rating: 2
This is one reason why cars (Tesla aside) don't use Lithium-Ion batteries: Too much risk of thermal runaway.


RE: propagation of fire to adjacent cells??
By Samus on 2/11/2013 12:43:26 PM , Rating: 2
The difference between Tesla and other manufactures (even GM had problems safely securing the Volt battery packs upon impact) is that Tesla understands Lithium chemistry, and the others do not.

Tesla was a battery company before a car company. The first thing they engineered were lithium pack designs and electronic controllers. They don't make the motors (Mitsubishi) and their first car (Roadster) was almost entirely made by Lotus.

Tesla fitted the Elise with their batteries , speed controller, PEM, and Mitsubishi's motor.

Tesla is a battery company. Boeing is an aircraft manufacture. Boeing outsourced an unprecedented amount of manufacturing for the 787, perhaps they should have outsourced the battery design instead of just buying a pre-made, first generation battery from the Japanese.


RE: propagation of fire to adjacent cells??
By DockScience on 2/11/2013 1:03:35 PM , Rating: 2
The DID outsource the battery design... to France's Thales.


By mars2k on 2/12/2013 12:30:51 PM , Rating: 3
First....we chainsmoke, zen we make ze batteries


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.
http://en.wikipedia.org/wiki/Lithium-ion_battery#S...

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.
http://en.wikipedia.org/wiki/Ford_Capri#Ford_Capri...

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: http://www.ev-power.eu/LiFePO4-small-cells/WINA-Li...
Electronic Cool Liquid: http://solutions.3m.com/wps/portal/3M/en_US/Electr...

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


By Alexvrb on 2/11/2013 11:59:32 PM , Rating: 3
GM's and their battery partners understand Lithium chemistry quite well. They have never burst into flames in normal use like the ones used on the 787. They also have only caught fire in abnormal circumstances. NHTSA wrecked it (actually they wrecked three and only one caught fire) damaging the battery, let it sit in a garage for a week still damaged/compromised, letting the coolant drain out of said damaged battery, without at any point discharging the battery as recommended? I don't understand your point. I'd say its a given that negligence causes problems.

Regardless, it caused enough bad press (even though it was not a real-world crash event) that they further reinforced the area around the battery to better shield it from damage during such tests. In addition, the Spark EV is going to be using Li-Polymer. It doesn't have quite the power density, though. If they can improve Li-Po enough it might end up in more vehicles.


RE: propagation of fire to adjacent cells??
By alpha754293 on 2/11/2013 12:46:13 PM , Rating: 2
Except for Tesla, Ford, Nissan, Chevy, Fisker, Toyota, Honda, Volvo, Land Rover, BMW, Mercedes, Volkswagen, Porsche, Infiniti, Lexus, Audi, etc., etc., etc.


RE: propagation of fire to adjacent cells??
By protomech on 2/11/2013 2:40:58 PM , Rating: 2
Porsche and Lexus are still using NiMH for their 2013 models. The 2014 Porsche 918 will use lithium-ion batteries.

But yes. The automakers are increasingly switching to lithium-ion for cost, durability, and packaging reasons.

Proper safety design can mitigate (not eliminate) the risk of thermal runaway .. just like proper safety design can mitigate (not eliminate) the risk of gasoline fires.


RE: propagation of fire to adjacent cells??
By alpha754293 on 2/11/2013 11:29:17 PM , Rating: 2
I would have thought that with the latest Prius going to Li-ion that Lexus would have followed suit already.

The other big reason why the automakers are switching over to Li-ion: mass. There's a HUGE push from ALL of the OEMs to make the vehicle lighter in order to meet the upcoming fuel economy standards/requirements.

Well...if you mitigate it enough, it can EFFECTIVELY be eliminated. There are things that you can do that where you start looking at the failure modes and effects analysis and start to think of things of how you can almost entirely prevent that mode of failure. I don't think that I've heard of a case of the kind of Pinto gasoline fires now that they put the gas tank IN FRONT of the rear cradle.

In fact, people (safety, regulatory, engineers) are so paranoid about potential failures of the fuel systems that it is probably one of the safest and most robust systems that exists on a car today. It's borderline ridiculous, but people are so paranoid about it that they overengineer the crap out of it.


By protomech on 2/12/2013 2:08:19 AM , Rating: 2
The latest Prius is still NiMH (Prius, US Prius V, Prius C).

2015 Prius is rumored to go lithium-ion. Guessing Toyota wants to get the kinks worked out with the Prius+ and the plug-in Prius before they move their mainstream Prius to the new chemistry.


They wouldn't take his help...
By Daneel_ on 2/11/2013 11:03:25 AM , Rating: 5
Elon Musk must be feeling pretty smug right about now.




RE: They wouldn't take his help...
By GulWestfale on 2/11/2013 11:53:49 AM , Rating: 3
i think he feels that way most of the time anyway.


By rudolphna on 2/11/2013 12:35:45 PM , Rating: 3
And in most cases, justifiably so.


RE: They wouldn't take his help...
By Sazabi19 on 2/11/2013 12:02:35 PM , Rating: 2
But aren't the drivers of hybrids and alternative energy cars the leading cause of smug?


RE: They wouldn't take his help...
By mrwassman on 2/11/2013 12:28:17 PM , Rating: 1
yes


By seamonkey79 on 2/11/2013 6:01:05 PM , Rating: 2
I heard the smug in LA was so bad they had a news report about it and it blanketed the city in smug clouds 0_0


The hair trigger.
By drycrust3 on 2/11/2013 4:38:29 PM , Rating: 2
quote:
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.

I think the investigators have got the wrong end of the stick. They are saying the battery cells are the problem, not the environment, but I think the environment is the problem, not the battery, or rather, the battery isn't the right one for the environment.
As I understand it, this battery has a nominal voltage of 30 volts, and each cell has a nominal voltage of 3.7 volts, meaning the entire battery consists of just 8 cells, so all cells in the battery showed the same signs failure.
According to one media report, Japanese Transport Safety Board investigator Hideyo Kosugi said "I'm sure that too much current or too-high voltage has gone to the battery".
(Link removed to avoid spam detection)
According to the Yuasa spec sheet for this battery, the maximum "operative ambient temperature" for each cell is 65 deg C. (See their spec sheet here: (link removed to avoid spam detection))
As I see it, as the internal temperature goes up, so the resistance of the internal insulation drops, thus the internal leakage current increases within each cell. Normally the heat generated by the internal leakage is so small that the battery as a whole can dissipate it happily, and there isn't a problem.
If, however, due to some environmental factors the battery cells aren't able to dissipate the internal heat as fast as it is generated, e.g. an alternating high discharge current and then a high charge voltage are applied to the battery, or the battery cells are tightly packed in a poorly ventilated area, so the internal temperature rises above 65 deg C, then you could one of those endless loop problems.
For example, say a sustained cycle of load and charging is placed on the battery and the raises the internal temperature rises above 65 deg C, so the leakage current also rises to the point the heat generated by it is faster than the battery can dissipate, then you would have a cascading effect, where the rising temperature allows more the leakage current, and the increasing leakage current raises the internal temperature, and you would get an almost impossible to stop situation.
It may well be this battery could, in just seconds, go from being "a bit hot" to erupting like a volcano.




"And boy have we patented it!" -- Steve Jobs, Macworld 2007

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