Originally posted by CabaHence, then electrical energy you get is equal to sum of all other kinds of energies required to maintain this potential difference. In most occasions that's chemical energy.
A car (any) battery is essentially a device that produces lots of electrons at one point (one of it's termials/electrodes whatever) and not so many at another point. This gives you a potential (voltage) difference between the two points.
Electrons don't like each other so they want to go where there is less of them so when you create a path to such a place (el ...[text shortened]... is to maintain the potential difference through other energy means, like chemical reactions.