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I think the bigger overarching problem would be Boeing subcontracting out so much of the design to 3rd parties. For one, a fire at Hamilton Sundstrand, in the lab that designs the battery, not a good start. That giant CATIA model of the airplane assemblies doesn't convey knowledge about design experience that can only be retained in the brains of employees.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
What is there in an individual lithium ion battery cell that can disrupt the container releasing more energy than the equivalent volume of steam superheated with what ever electrical energy the cell had when it failed? Brown's gas ?
The electrical industry long ago solved the problems of thermal decomposition or organic insulators.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
I think it has to do more with *rapid* release of energy, ie the entire stored electrical potential in the cell being dumped into a very small area in less than a minute. The damage resembles that caused by an exploding LiPo that has been overcharged, as the electrolyte is also flammable when heated it acts like a BLEVE (Boiling Liquid Expanding Vapour Explosion)
See the damage at the Tchernobyl plant for an idea of how violent a mere steam explosion can be...
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
The electrolyte in lithium ion batteries isn't water-based. It is a flammable organic solvent (not unlike gasoline) doped with fluoride salts.
So besides the electrical energy in the battery (which is considerable, that's the whole point) there is the heat of combustion of the electrolyte. The usual failure mode is that the cell goes into thermal runaway, converting the stored electrical energy to heat, which boils the electrolyte and causes it to spray out. The spray is already heated above its flash point so on meeting the air it ignites. Once one battery in the pack starts spewing flame, it can set off the others, because even a healthy Li-ion cell will go into thermal runaway if you heat it up enough.
Also the smoke contains hydrofluoric acid, so it is wise to resist the temptation to set your collection of dead Li-ion batteries on fire.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
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Posts: 1546
In systems that dripped or spewed burning liquid, a Davy screen was used, which cooled the liquid as it passed through blocking the flame.
I havent be able to find out what the solvent is in these batteries.
Perhaps in futur designs combustible gasses and battery ejaculates could be rerouted to the intake of the the engines where it would be burnt just as bird feathers are.
The intakes may be a good place to locate those batteries, at least controlled cooling could be applied.
Years ago British planes flew radioactive material in the wingtips to keep it away from the pilots.
Registered Member #3272
Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101
I am using 16 50AH Lithium Iron Phosphate batteries to build a pack to power my telescope and computers in the field, these guys here:
A friend designed a battery management board for these guys and they have been putting them in motorcycles. For fun they took one of these batteries and threw a metal rod threw one, it filled the block with smoke.
Lithium rechargables are very picky beasts, charge them too high and they are toast, let them discharge and they are toast, too much current and they are toast. So this airplane problem could be a defect in the batteries like sony had (Metal shaving got into the mix) or it could be the battery management system and it let one cell drop below 2.7v.
Batteries are electro-chemical. They require chemical reaction for power, when cold it just does not happen as easy so the capacity drops big time. Warm them up and they will have full power. Some packs for vehicles have heaters built in to keep them warm in cold climates.
Registered Member #9832
Joined: Fri Jan 25 2013, 05:40PM
Location: Elbridge, New York, USA
Posts: 1
I've been experimenting/researching Lithium systems actively for the past few months. (I was stunned/infuriated that the price for a Porter Cable tool Battery is nearly $100, and decided to retrofit some dead Ni-Cad ones to Lithiums - Way not as simple as it seems at 1st look)
One of the many nastys of the Lithium animal is that if overdischarged the Lithium compounds in the electrolyte will disassociate and produce metallic lithium. The next (or some cycles into the future) charge cycle the metalic lithium then causes an internal short, subsequent overheating and explosion. This problem is compounded if the cell is in a series/parallel battery (which it almost always is).
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
macona wrote ...
I am using 16 50AH Lithium Iron Phosphate batteries to build a pack to power my telescope and computers in the field, these guys here:
A friend designed a battery management board for these guys and they have been putting them in motorcycles. For fun they took one of these batteries and threw a metal rod threw one, it filled the block with smoke.
Lithium rechargables are very picky beasts, charge them too high and they are toast, let them discharge and they are toast, too much current and they are toast. So this airplane problem could be a defect in the batteries like sony had (Metal shaving got into the mix) or it could be the battery management system and it let one cell drop below 2.7v.
Batteries are electro-chemical. They require chemical reaction for power, when cold it just does not happen as easy so the capacity drops big time. Warm them up and they will have full power. Some packs for vehicles have heaters built in to keep them warm in cold climates.
Same goes with lead acid and Ni-Mh, its just that the consequences have gotten steeper for mistreating the battery, and it tolerates less mistreatment.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
If you ask me, the market is wide open for "intelligent" Li-Ion cells that include within the structure pressure and electrochemical sensors that detect electrolyte decomposition and apply a controlled shutdown.
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Battery problems on Dreamliner
