A Boring Dystopia

Yes, if you run hundreds of amps through metal it gets hot, but that's not electrocution which is what the person you're replying to is talking about. You can't really electrocute someone with less than about 50V because the human body has too much resistance. You can try it yourself; lick 2 fingers and touch both poles of a car battery; you won't feel anything because your skin has too much resistance for 12V to meaningfuly pass through. The only danger a 12V battery poses is if you short it with a piece of metal then that metal will get very hot and often hot enough to melt or explode both itself and/or the battery. But as far as torture goes a car battery is a very round about way to heat up a chunk of metal when you could just use a torch or something.