Although most parallel hybrids incorporate an electric motor between the vehicle 's engine and transmission , a parallel hybrid can also use its engine to drive one of the vehicle 's axles , while its electric motor drives the other axle and\/or a generator used for recharging the batteries .
Plug-in hybrid cars that use a gas engine exclusively for recharging batteries-rather than directly powering the wheels-are also called Extended-Range Electric Vehicles or E-REVs .