Q: I read your answer concerning "Would The Prius Get Better Gas Mileage If It Weighed Less?". It was very interesting and I agree with your discussion but I'd like you to go a step further. The thing that is confusing about hybrids has to do with their efficiency. It seems to me that using an internal combustion engine to charge the batteries which power the electric motors that move the car would be less efficient that moving the same car with the internal combustion engine. I recall someone's theory having to do with "Conservation of Energy". Applying the same technologies that maximizes the efficiency of the gas engine as a "charger" could also make it a better "mover". Right?
A: You are correct, charging the batteries onboard with an IC engine and then powering the wheels with an electric motor is inherently less efficient than just gearing the IC engine to the wheels. That’s why most hybrids have some way of doing either or both.
Two compelling reasons to use batteries:
In a conventional hybrid, the batteries are on board to capture energy during regenerative braking, using this energy (normally wasted as heat in the brakes) to accelerate the car later.
In a plug-in hybrid, the batteries are recharged by the grid. A PHEV, if driven for short enough distances to not drain the batteries, may never consume gasoline.
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