A kinetic energy recovery system (often known simply as KERS) is an automotive system for recovering a moving vehicle's kinetic energy under braking. The recovered energy is stored in a reservoir (for example a flywheel or a battery) for later use under acceleration.
Kinetic energy recovery system - Wikipedia, the free encyclopedia
Wikipedia is a great source of information for people who have never heard of it. Most use a flywheel for simplicity and weight savings rather then charge a battery or capacitor.