Regenerative braking is an integral part of every hybrid electric vehicle. Here, deceleration and braking energy is converted to electrical energy to keep batteries charged. Hydraulic hybrid trucks and buses recoup energy by pressurizing a hydraulic fluid that's stored in an accumulator, and then use this energy when extra power is needed. There is third type of regenerative braking where recouped energy is stored in a flywheel revved up at high rpms
Read Article