An electric car battery can give 400-800 volt. Enough to kill or cause serious burn damage, unless the time of exposure is really short. Over 500 Volt is classified in medicine as high voltage accident. Carelessly manipulating this batteries at home is not a smart idea.

Who says I'm careless?

And 400V is pretty standard in homes here too (though to be fair one individual phase is 240 but still..). If you have a heat pump or a sizeable electric stove you will already have 400V.