No. The KERS that was featured on Racecar Engineering is powered via the gearbox. When you want to brake, you connect them both, KERS spins up (via a CVT), takes up the amount of energy that can make the car accelerate with ~30 KW later by spinning up very fast (65k rpm i think, since that way it can have enough energy while still being light). When you need the power (or need a pass), you release it again via a CVT, slowing it down and accelerating the car. IT's just a mean to store the kinetic energy of a car that would be dissapated in the brakes otherwise.