Has anyone ever tried using a "front hub" light generator to charge the bike batteries....or have two batteries on a switch, charging one of the batteries as you roll down the road, and the other to power your ride?
That will work, the only problem is you will never get back what you put in. If it worked well every car , truck, train , refrigerator would have something like that. In ANY system there is always some loss from friction, resistance in wires etc.