How does regenerative braking turn a stop into charge, and how do hybrids use it?

Regenerative braking turns a stop into charge by making the car's electric motor work in reverse, as a generator. Regenerative braking recovers energy by converting a moving vehicle's kinetic or potential energy into a form that can be used at once or stored. In a car, the brakes typically drive an electric motor in reverse, which effectively turns the traction motor into a generator and recaptures energy that would otherwise be lost as heat. That power can resupply a battery or a capacitor and be used later to help propel the car.

Ordinary friction brakes do the opposite: they turn the excess kinetic energy into unwanted, wasted heat through friction. A regenerative system can recapture around half of the energy lost when a car brakes, which means a 10 to 25% efficiency gain.

Hybrid cars make good use of it. A hybrid vehicle uses two or more distinct types of power. In a hybrid electric vehicle the electric motor is more efficient at producing torque, while the combustion engine is better at maintaining high speed. Even mild hybrids, which use a compact motor for stop-start and extra power in acceleration, also generate on deceleration, which is regenerative braking.

It does not replace the brake pedal. The regenerative effect is limited, so mechanical braking is still needed for substantial speed reductions and to stop the vehicle, though the system can significantly extend the life of the brakes.