Originally Posted By: ZZman
Do you think a generator alone could keep a battery charged or increase range a great deal or don't they make enough juice?
Depends on the generator! The motor and generator are each maybe 90% efficient, so 0.9 x 0.9 = 0.81, or 81% efficient conversion from diesel engine crankshaft output to electric motor output. If the car is shaped like a Prius with low air resistance, it might only need 15 hp to cruise at highway speeds. So 15 hp / 0.81 = only 18.5 hp needed at the diesel engine to break even when cruising.
To run the motor, the generator's output would have to be 15 hp / 0.9 = 16.7 hp. One hp is 746 watts, so that would be 16.7 x 746 = watts 12,433 watts, or 12.43 kW. A large battery could easily soak up another 10+ kW when charging. So a 25 kW generator could charge the battery and cruise the car at the same time.
But for higher efficiency, the diesel can be connected to the wheels as well through a CVT transmission with two inputs and one output. This bypasses the 21% efficiency loss of mechanical to electric to mechanical conversion shown above and replaces it with just a few percent loss in the transmission. That way the electric motor can serve as the generator, saving weight and space. When the car is stopped while charging, the wheels are disconnected and the diesel keeps spinning the motor to charge the battery.