PPRuNe Forums - View Single Post - 787 Batteries and Chargers - Part 1
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Old 15th Mar 2013, 17:16
  #991 (permalink)  
Lyman
 
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,123
I think you have not understood the nature of the chemistry involved.

"Inerting" the enclosure, by eliminating Oxygen, accomplishes nothing. This battery will spontaneously ignite without the presence of Oxygen. The electrolyte is an organic, and burns fine without ambient O2. At one time it was believed that because some Oxygen is produced in the burning of the electroyte, and the LithiumCobaltOxide, that it is somehow self sustaining, and that is why it resists extinguishment. That is a myth.

If you would like a reference I would be happy to supply one, but instead, you may want to read the paper that was the standard in 2011.

I have linked it here before.

"Burning" is not the problem, anyway. Temperatures in a runon cell push 3000 degrees, far hotter than any Fire".

The problem remains, IGNITION. NOT Oxygenation....Boeing still have a humongous obstacle ahead, to prove that retention of a volatile Battery system is worth allowing something that has never before been allowed, Fuel, and Ignition, present on an aircraft. If some wag wants to bring up Engines, have on. Kerosene does not spontaneously ignite.

It's an interesting discussion, but the basic problem, still, is reliability, and the regulations that do not allow fire.

The specific regulations won't allow even the production of excess pressure and temperature. Boeing needs to get around that, isolation in a box does not satisfy that rule. Not yet, anyway.

I think a fair question is what happens to the ejecta from the box? The composition and construction of the vent tube must sustain temperatures approaching 3000 degrees intermixed with carbon, ash, molten aluminum, and dense toxic smoke. All this is to be dumped along the belly of a plastic aircraft possibly hours from any place to land? Into an OXYGEN rich environment for, how long? twenty minutes? Can you think of a better way to ignite CFRP? Super heated oxygen starved solvents, metals, and vapors, blown into a 400 knot jet of Oxygen? Has anyone thought that through?

Convince me. The benefit of the doubt has passed away, and was given a burial in January.

For one second, Ian, do you think this scheme would have passed original certification?

Last edited by Lyman; 15th Mar 2013 at 19:40. Reason: add detail
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