"The electric car was so badly damaged in the crash that
firefighters could not isolate the electric power meaning crews
had to work carefully around the electrics because of the
potential risk of electric shocks which could have caused a
I hadn't thought of that failure mode.
I'd have expected there to be some sort of automatic battery isolation
device if the car was subject to high g impact forces.
It isn't all that different to working on a petrol car where the fuel
tank has been ruptured where the first spark could well be fatal
(although they try to make petrol tanks so this doesn't happen).
Any energy dense power source is a real menace when compromised.
Surely if airbags can be set off by a certain g force it should not be
beyond the wit of electric car manufacturers to include a "g force fuse"
in the battery circuit, so isolating the batteries in the event of a crash.
There is a lot of difference between breaking the circuit for a fuel
pump and that for an electric car.. The fuel pump will use 12V at a few
amps; an electric car might be using 100V at 500 amps. If you try to
break that with an ordinary switch you will get an unquenchable arc
between the switch contacts.
A "g force fuse" would have to be designed break the circuit and quench
A not insurmountable problem. High voltage breakers have an arc
quenching barrier, which drops into place when the breaker opens. Even
the fuse in a 13amp plug top has a sand filling to quench the ark.
DC is more inclined to arc, but there are methods which have been in
use for donkeys years to deal with it and for much higher DC currents.
If it's not passenger-operated, then its position in the car is
irrelevant. However, if it really is there, that's one of the worst
possible places for the emergency services if they need to give it a
Isn't the switch Harry describes the one which detects the high G force
and cuts the power automatically in the event of a crash? So being next
to the battery is good, but doesn't need to be in a "convenient" place.
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