The cutoff is to stop the electricity from leaving the battery, and electrifying the rest of the car. Nothing more fun that getting electrocuted just touching a car. F1 cars are also Hybrids, and if you watch F1 drivers exit a the car after a crash, they do a little hop off the car. Making sure not to touch the car and the ground at the same time. They also have little indicators that show if there is current running into the car's body. I will venture that an F1 hybrid system is at least as advanced, if not more-so, than a common consumer hybrid system. At the least, I wish Commercial EVs had that same electrification indicator.
Cutting that wire is largely, to de-power airbags and the like. Airbags DO go off unexpectedly, and can inure a responder quite effectively. Cutting the power is a normal step in any big motor vehicle incident, EV or ICE.
Tesla and others do publish all this information with nice diagrams and handy mobile apps, and we study them. However, this doesnt fix the problem of the Huge Energy load in the battery itself. Even if that energy cant get out of the battery through wires, it can still burn like crazy inside (and outside) the battery case(s).
Im a Vol Firefighter in a Major City Suburb with lots of highways and tons of crashes. We get 2-3 car fires and passenger extractions per month. The first question we ask on the way out is "Is this an EV?"
We need to know this because EVs trigger the rollout of Water Tankers from surrounding towns, as many as we can get. Usually a Water Shuttle has to be set up. Not many Fire Hydrants on Highways, and EV fires require A LOT of water, like several house fires worth...
Here is some external detail on this - https://www.businessinsider.com/tesla-crash-fire-lithium-bat...
Also, we need to start calling more manpower. EV fires burn a very very long time while ICE fires are usually put out in the first few mins, and with 1 engine's 1000gal tank water.
Adding to this, the fire is usually under the car, and quite hard to get too. We are very good at opening locked car hoods and cutting metal to get at the fire, but when its deep in the guts of the thing, its impossible. At my department, we have started working on ways to jack the car up safely while its on fire so we can get water onto it. Trust me, its even harder than you would think...
The Standard Operating Procedure is to put water on the car and surrounding area so that nothing else catches on fire, but basically we have to let the thing burn out, and that can take hours and hours...
EV car batteries do not rely on the environment for their fires to burn. The fuel brings its own oxidizer, and it doesnt need anything else. We can put out Liquid Fuel fires by robbing the oxygen or removing the heat(thats what the water does), but once EV fire gets to a particular point of no return (which it arrives at very quickly) there is really nothing that can be done to stop it, just
make sure it doesnt get any worse...
Here is the current thinking from the NFPA (firefighting safety and standards organization in the US), you'll see EV car fires are long on problems, but even the most focused minds in the US Fire Prevention industry are short on answers at this time.
https://www.youtube.com/watch?v=Sp3WvKON_W4
Cutting that wire is largely, to de-power airbags and the like. Airbags DO go off unexpectedly, and can inure a responder quite effectively. Cutting the power is a normal step in any big motor vehicle incident, EV or ICE.
Tesla and others do publish all this information with nice diagrams and handy mobile apps, and we study them. However, this doesnt fix the problem of the Huge Energy load in the battery itself. Even if that energy cant get out of the battery through wires, it can still burn like crazy inside (and outside) the battery case(s).