Boeing lithium batteries

A380 RAT.. under the port wing (#53)

The thing you never want to see in flight.

Best regards, Spehro Pefhany

Yes, I saw this. With how tightly the cells are packed, this is pretty ridiculous. Given how strongly certain Li-ion cells can burn, it was crazy to think that failures would not cascade in a tightly-packed battery system. Whoever did that part of the analysis should be shot.

Jon

It's dead easy- we do it in some airborne battery systems (not Li) to prevent thermal runaway from cascading, but it costs some size and weight.

The fire did not propagate to all the cells. Only one other cell adjacent t o the cell originating the thermal runaway burned up, that would make one o ut of the three adjacent to it. For all they know that cell could have been in what's called the onset stage of thermal runaway itself, which can last for weeks before the internal reactions start to accelerate, and may not b e detectable by any of the external sensors.

OK, this is different than what I'd got from some other media, including some technical sources. They seemed to all say that most of the cells were severely damaged, and the photos seemed to support that. If only one other cell had a runaway, then they almost have the protection right. The cells seem to be pretty closely packed to me, but it does look like there is some kind of padding between them.

Jon

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Right, for the Boston JAL incident NTSB determined the runaway originated i n cell 6 and only cell 3 went into sympathetic combustion. The cells were a rranged in two columns of four where 3 and 6 were in separate columns next to one another. There are insulator materials can handle temperatures way h igher than the 500oC heat of this fire and are quite thin. I'm pretty sure Boeing knows quite a bit about fire containment, just not corrosive electro lyte containment. But then again this fire was extinguished and not allowed to run its course.

How do they deal with Li fires anyway? Water or CO2 don't cut it.

Jeroen Belleman

The Logan FD is reported to have used Halon.

IIRC the electrolyte acts as an oxidizer in a fire. So halon wouldn't have done much until the oxidizer was depleted. This means the only way to extinguish a fire in these is to get rid of the heat :( -f

Right- they were probably using to prevent fire in nearby objects and it was all they had.

Looks like Cessna is on the right track here:

While test labs do not fly they certainly have vibration, shock, altitude, vacuum test facilities, and some have combined altitude/vacuum with shock and vibration facilities. So now the question is did they specify such testing? Failing to specify both extensive shock and vibration testing would clearly be an engineering slip-up at a minimum, more likely a management foul-up for not understanding the importance of these rather expensive tests for this application.

guess

flying

Sounds like you have done some test engineering or at least been close enough to understand. I did 13 years of test at Hughes once upon a time.

?-)

Yep, the fire extinguisher of choice is liquid Argon or liquid Neon. Also for Magnesium fires and Thermite. It takes a lot in either case.

?-)

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IIRC it was about 1 cubic foot. Seriously high energy density.

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One thing is clear as he**, the general public will never get a clear accounting of the cause. I doubt that even forensic engineers other than the investigative team will ever get adequate information.

?-)

On a sunny day (Mon, 11 Feb 2013 22:45:21 +0100) it happened Jeroen wrote in :

In a recent paper I did read Navy uses water vapour, as that cools the cells down. From: Lithium-Ion Batteries Hazard and Use Assessment pdf is on the internet, google,

The FAA studied suppression of lithium-ion batteries with water and Halon 1211, as these are typically available in hand extinguishers aboard commercial aircraft.172 As a first choice, the FAA recommends the use of water to suppress fires involving notebook computers, because water will both extinguish flames and suppress thermal runaway propagation. As a second choice, the FAA recommends using Halon 1211 to knock down flames, followed by deluge from available water sources (such as bottles of drinking water). Halon 1211 alone will not prevent

:-)

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Water is a strong oxidizer for Li. Pouring water on Li metal will ignite it, not extinguish it!

As someone else in this thread pointed out, it's not even necessary to add any oxidizer. In a charged battery, fuel and oxidizer are conveniently close together in a single little package. While in less efficient battery technologies, thermal mass and presence of inert materials was sufficient to prevent fires, modern batteries have energy densities that are high enough to ignite if breached.

I believe that to make them safe in this respect, oxidizer and fuel should be stored apart.

Jeroen Belleman

On a sunny day (Tue, 12 Feb 2013 10:58:47 +0100) it happened Jeroen Belleman wrote in :

first choice, the

computers, because

As a second

deluge from

will not prevent

Direcltly on Li, but pouring it on overheated batteries may stop the fire from going to the next (not yet broken) one. Who am I to argue with FAA?

If I ever had to stop a fire in a laptop on board, and survived doing it this way, and there WAS an investigation, this is on google. They must have run tests, so I'd use water. (Not that you have much choice, little Wodka bottles would likely not be a good idea ;-)

Yes, I think fuel cell is the way to go, after all plenty of fuel, and air no problem either. Airbus is working on that.