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Registered Member #3272
Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101
Conundrum wrote ...
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.
That will significantly raise the cost of the batteries. BMCs are all you really need, most of the fires that you see lately are caused by people not incorporating them.
Like this:
And there are some applications where you do not want auto cutout when the batteries get low like remote controlled planes and helis as well as things like full size motorcycles.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
Elon Musk is saying on this issue that their battery is packed too tight, if you have a big battery pack then you can't get the heat out from the middle due to cube-square laws. Sounds like something they could conceivably fix, although it will probably cost weight and volume.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
From here:
"Unfortunately, the pack architecture supplied to Boeing is inherently unsafe," writes Musk in an email to Flightglobal.
"Large cells without enough space between them to isolate against the cell-to-cell thermal domino effect means it is simply a matter of time before there are more incidents of this nature," he adds.
Both Boeing and Tesla use batteries fueled by lithium cobalt oxide, which is among the most energy-dense and flammable chemistries of lithium-ion batteries on the market. While Boeing elected to use a battery with a grouping of eight large cells, Tesla's batteries contain thousands of smaller cells that are independently separated to prevent fire in a single cell from harming the surrounding ones.
"Moreover, when thermal runaway occurs with a big cell, a proportionately larger amount of energy is released and it is very difficult to prevent that energy from then heating up the neighboring cells and causing a domino effect that results in the entire pack catching fire," says Musk.
An aerospace-capable version of Tesla's battery has been developed for use in SpaceX's Falcon 9 space launch vehicle. SpaceX, also owned by Musk, competes with Boeing/Lockheed Martin joint venture United Launch Alliance for customers. Boeing has thus far declined offers of assistance from Tesla and SpaceX, says Musk.
"They [Boeing] believe they have this under control, although I think there is a fundamental safety issue with the architecture of a pack with large cells," writes Musk in an email. "It is much harder to maintain an even temperature in a large cell, as the distance from the center of the cell to the edge is much greater, which increases the risk of thermal runaway."
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Boeing has redesigned the battery system by putting in a stainless steel box in case it blows, and if it does, they will have it vent, to the outside of the aircraft.
" Perhaps in future 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."
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
radiotech wrote ...
Boeing has redesigned the battery system by putting in a stainless steel box in case it blows, and if it does, they will have it vent, to the outside of the aircraft.
This has been common practice in the marine industry for decades, in fact I'm pretty certain it's part of 'lloyd's Rules' for marine insurance. It's also common practice on caravans, etc.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
In the Kraft process (paper making) a collection the worst gasses was routed to the intake of the lime kiln where it was burned to prevent odors that could be smelled for miles. We called it the NCG (non condensable. gas) system.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Steve Conner wrote ...
Hence, Murphy's law of energy storage systems: The higher the energy density, the bigger the bang when (not if) it goes wrong.
Precisely ... !!! (especially for us drone maker/operators, get ready! )
radiotech wrote ...
" Perhaps in future 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."
This is so funny, becuase its true...
radiotech wrote ...
Risk management is a wonderful science.
Risk management / failure analysis is wonderful and really cool, but only when im not the one bleeding and dying, from some dumb idiots F'up...
Windscale, chernobyl, coloumbia SST, Titanic, love canal, Union carbide--Bohpal, india... all those rivers that caught fire in the 70's... and the list goes on.
i think i made a more thoruogh list afew years ago.
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Battery problems on Dreamliner
