Another Tesla Fatality with Fire

Another great example of the need to be careful as to how you analyze statistics. The most striking thing that sticks out here is that the lowest rates are all expensive luxury cars, and all highest rates are among the cheapest cars you can buy. So, what does that mean? The luxury automakers would tell you (as Tesla does) that it means their cars are better built and safer. I would guess that is true to some extent. What else could it mean? As was mentioned above, wealthier people will be driving the more expensive cars. I would think they would get in less accidents. Wealthier people would be older and more careful. What would also be a factor is that many of these cars are more babied by their owners. Maintained better, in some cases only driven in better weather, etc.

So, when Elon says that you are 6 times (or whatever the figure is that he uses) less likely to be injured or killed based on per hours driven statistics, be careful about what that really means.

Back to the main point here, I don't think you are any more likely to burn in a Tesla crash than in a gas car crash. That is not based on any good facts, just from what appears to be logical to me. It seems that gasoline would be more likely to burn in a crash than batteries. I could be very wrong. And yes, we are hearing about every Tesla fatality and fire because Teslas are the IT car with the new technology, and everyone wants to tear down successful people and companies at every chance they get.

 

In a severe crash everything moves! It's only a question of by how much. Half a ton of batteries stopping from 15 or 20 metres a second in perhaps a tenth of a second is going to be damaged. Musk cannot stop it, his engineers cannot stop it, all the King's horses and all the King's men cannot stop it. Far from being impossible, it is impossible to STOP it happening.

The questions to be answered are whether the distortion or crushing of a cell will cause overheating and will that cause the adjacent cells to do the same.

 

Are you claiming that the battery blazes which took place after severe crashes did not occur? That is the implication of your statement, is it not?

 

This oft-repeated argument is getting a bit old by now. The oldest production Tesla cars are now 10 years old, certainly long enough to properly assess the danger of fire... or in this case, the relative lack of danger!

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No.

 

David - how do you know any of this? Methinks you are just making stuff up.

If you want to avoid vehicle fires - don't drive a gasoline car.

 

Well, we can argue causality I suppose. A considerable impact inevitably involves rapid deceleration and that is what caused distortion of the battery pack as well as the rest of the vehicle. You certainly wouldn't damage the battery pack by hitting the brakes too hard!

I am in full agreement with you that a severe impact is needed before enough damage is done to trigger thermal runaway however.

You are wrong about gasoline cars burning, even after severe impact, though. Despite Hollywood's depiction of an impact resulting in a firebomb, this actually doesn't happen, and even a fire following the crash is rare. Those that do occur do so usually due to a damage to the electrical system causing a short circuit, heating up the conductors and melting the ignition before igniting it.

In order to stage a 'Hollywood' explosion, significant technical equipment is needed including explosives to disperse fuel in containers placed in the passenger cabin and the timed ignition of propane-air mixtures etc.

I would not be surprised to find that the probability of ICEs going on fire is pretty well unrelated to the severity of the crash after a certain point, but I think the probability of fires in battery cars would go up pretty well directly with the speed of impact.

 

Your claim that Tesla battery packs are easily ignited - is baseless.

 

Er... Here are some Tesla cells being crushed.



I was a bit surprised how quickly they ignited. At the point when they ignited, the crushing had only just split the can. Given that the 2170 cells are bigger and contain more energy I expect them to be rather more fragile.

Incidentally, I estimated how much force you'd have to apply to a half ton of battery (500kg) whizzing along at 30 meters a second (A bit less then 70mph) in order to stop it in 100 milliseconds. This is a deceleration of 300 m/s squared - about 30 g - and the force required to do it is 150,000 Newtons.

What does a force of 150,000 Newtons imply in terms of everyday experience? Well, it is pretty near a fifteen-ton weight applied to the battery for that tenth of a second of deceleration.

If this is distributed over all the batteries equally, they might well stand it OK, but it is more likely that the cells at the front of the pack will stop much faster and the ones behind will carry on. In other words, you'll get a wave of crushing moving from front to back until all the kinetic energy is dissipated.