Question on car safety
As well all know, the P2 cars have the main battery located inside the trunk, basically just behind the rear bumper. How safe is this if the car is rear ended in a more severe crash? Could the battery catch fire?
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That's an interesting point, and one that came immediately to mind when I first saw the P2 battery location. One would imagine some sort of failsafe strong zone around the battery box could be implemented, although not sure how effective it would be as it's so close to the rear crossmember & surely the crumple zone would be compromised in this case too?
Having said that, some of the salvage rebuild channels I watch on Youtube have shown a fair few nasty impacts where the battery has been crushed/broken on various cars & it hasn't resulted in a fire. I think when the battery gets smashed it tends to leak all it's electrolyte fairly quickly and the plates within become less capable of producing power/heat even if they're mushed together somewhat. I think technically yes, an electrical fire *could* result from a rear impact to a P2 car but the chances probably are not significantly higher than a similar impact to any other car with different battery locations. Certainly interested to hear other's opinions and/or experiences around crushed batteries though. |
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I don’t believe it would catch fire |
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Great points, good to know acid batteries don't catch fire when crushed - I had the Tesla battery in mind but that's a different composition
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Lead acid I think are less likely. |
The lead acid accumulators (to give them their dullest name) are pretty robust, but they do depend on the electrolyte to provide the potential difference. Yes, they could split in a rear end whack but if they do split, they leak a bit of acid and don’t do a lot more afterwards. Naturally, the plastic they’re encased in is flame proof etc. They could provide a spark, but not much else.
With reference to the LiIon batteries that Tesla and others use, they are self oxygenating so cannot be put out byconventional means. If one remembers the triangle of fire, under thermal runaway conditions, they have heat, fuel and oxygen, more or less whatever you do so burn they will. In planning a LiIon test facility, I spend ages considering dousing with water, auto spuression systems and a whole lot of other kit, and in the end, I’m going to just place the batteries on a sled and basically jettison them if they go up and just let them burn. Consider that a V70 battery contains sufficient energy to run a starter motor for 90 seconds or so. A Tesla battery can move 2.4 tons of metal whilst keeping it cool or hot for 270 miles; there is a considerable difference in stored energy. |
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My money's on there being essentially no chance of an FLA (Flooded Lead Acid) battery bursting into flames upon impact of any amount.
The shining star of battery fires is a hydrogen explosion. Remember the Hindenburg? A spark at the right time in the right place can ignite lingering hydrogen and blow the top off a battery-voiding its warranty. In the case of a smash there wouldn't be much, if any, hydrogen lingering about, in the first place. If sparked, it would go up in a small, uncontained little poof. We ignited small amounts of hydrogen in science class as I'm sure you did. That sample had to be collected in a test tube. The polypropylene case, if smashed would allow the acid to drain out. Sulfuric acid isn't flammable. Buckled steel wouldn't contain any hydrogen produced were the engine and alternator to continue to run. SOURCES: Fire Departments, Insurance Companies, Automotive Engineers, Chemists, Battery Manufacturers SOURCES I CONTACTED: None of the above. |
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