use gravity to increase mileage

By Gary S.

The electric car would detect when you are going down hill and engage a generator to charge the batteries.
This will increase battery charging, which would increase the distance you can travel between charges or in a hybrid it would enable you to use the electric motors longer. Also it will increase resistance when going down hill to maintain a constant speed (safety).
guslack 08/22/2012
Been done for 1997 by Toyota with the original Prius hybrid sold in Japan