Comment Re:Why not put a generator on the engine? (Score 1) 35
Anytime you convert from one time of power to another you usually incur a ton of loss. Charging the battery with the engine or running the motors with the generator output, mechanical -> electric only to go back to mechanical pretty much destroys any advantage you get from running the engine more optimally.
Yes rail roads do this, but it is not about (fuel) efficiency, it is about torque / tractive effort (not a rail way engineer so I don't understand all the details differences )
With automotive hybrids it is more sensible to capture waste energy regen breaking, and help the engine when it is outside its power band, use the motor to provide the extra power needed for acceleration etc.
Use the motor more as the prime mover in situations like stop/go where engine power is hard to manage effectively at all, and there is otherwise lots of idling.