In a parallel hybrid, both the gasoline engine and the electric motor run the car. They both work to turn the transmission at the same time and give power to the wheels. The batteries store energy that is recovered from braking or generated by the motor.

Generated by the motor? How can that be? We learned earlier in the course that we have electric motors and electric generators that are two different things. But in hybrids the electric motor is both a motor and a generator. It can draw energy from the batteries to power the car (acting as a motor), or actually slow the car down, and in doing so, return energy to the batteries (acting as a generator).

Look at the diagram below.