A fire in a Tesla Model S electric sedan has once again placed a spotlight on the issue of lithium-ion battery safety.
The incident, captured on a now-viral video, occurred after the vehicle rolled down an off-ramp in a suburban area between Seattle and Tacoma, Wash. Soon after it stopped and the driver exited, the car's front end was engulfed in flames.
Tesla told Design News (a sister publication) in an email:
The fire was caused by the direct impact of a large metallic object to one of the 16 modules within the Model S battery pack. Because each module of the battery pack is, by design, isolated by fire barriers to limit any potential damage, the fire in the battery pack was contained to a small section in the front of the vehicle.
A CT scan image of a battery cell shows the breakdown of layers directly below an indentation. A recent report from Underwriters Laboratories Inc. said 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.”
(Source: Underwriters Laboratories Inc.)
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