http://en.wikipedia.org/wiki/Chevrolet_Volt In this series hybrid, engine and generator charge the battery and battery powers the motor, and can be made with components already available. The Ampera is claimed to do 175mpg (vs 40mpg on my current car). So I wonder why there aren't more cars like this already? Conspiracy? Is it really more efficient to use the engine as a generator to power a battery which powers a motor? Can someone show some numbers on this? If it is efficient, can this system be easily retrofitted on cars? Not like the Ampera/Volt where it can run from battery alone for 30+ miles, but enough battery to get the car moving and get the starter motor of the engine/generator going?