Exactly...

a liter of water goes in and a liter comes out so where the energy come from to charge the battery? The system is alway going to be less than unity. There's no excess power to charge the battery and power the vehicle.

Actually the water (if it is pure) electrolizes(is that a word?) into H2 and O2. The oxygen will combine to O2 just like in the atmosphere. The two Hs will combine to H2. With H and O you don't get any single atoms they immediately combine into two atom molecules.

Bruce