Putting in a 12V classical car battery makes a lot of sense. Sadly I don't remember all the details but: - You want a 12V circuit to be able to use "standard

Putting in a 12V classical car battery makes a lot of sense. Sadly I don't remember all the details but: - You want a 12V circuit to be able to use "standard car components". - You want to be able to power some components of the car separate from main battery in a way which can be powered from the outside (e.g. by replacing the 12V battery or attaching cables to it). - Just because a batter is well suited to drive a car motor doesn't mean it's also well suited to power a AC, entertainment system etc. Especially it might not be good at only powering such a system (i.e. it might not be good at such outputting some comparatively small load without to much peaks, loss or similar). I'm pretty sure you can find some resources on the internet which explain this is more detail with more technical knowledge :=) But just the fact that it allows you to "have a electric system like every other car" when it's not driving or charging makes it probably worth it for the manufacturer. And I would not be surprised that even if 12V Acid batteries go away EV still would have a secondary battery replacing it.