A CT scan image of a battery cell shows breakdown of layers directly below an indentation. A recent report from Underwriters’ Laboratories Inc. suggests that such dents in the casing are a possible failure mechanism for lithium-ion batteries. “The resulting high stress/strain will lead to a mechanical failure of the separator (with failure of the casing), allowing for direct contact between electrodes at a distance only a few layers below the casing surface,” the report says. (Source: Underwriters Laboratories Inc.)
You're right on the money, naperlou. Yes, Tesla has "fives" (best rating) across the board in NHTSA's safety ratings. And, yes, the methodology for the ratings is well established. I agree that the ratings agencies don't yet have a handle on how to characterize the relatively new phenomenon of lithium-ion failures.
Since the Tesla Model S batteries can be swapped out in a few seconds at their roadside stations, there must be some sort of quick release that would make it possible in an emergency to drop the battery pack and roll the car away from it, thereby saving the vehicle in case of battery fire.
Perhaps there should be a small, separate battery just for the purpose of driving the vehicle a few feet to get off of and away from the dropped main battery.
Chuck, Didn't Tesla get a top safety rating just recently for the S? This is a problem with EVs (and hybrids) that use Lithium Ion batteries. I am not sure that the testing agancies really know how to characterize the failure modes of these batteries. As I have mentioned before, there was an incident in China where an all electric cab of local manufacture caught fire and burned up the driver and passengers completely after a collision with a car that drove away. This is very worrisome.
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