[dahfizz]

The regenerative braking system is not complicated at all. In fact, it comes basically for free!

All that happens is you cut power to the motor but leave the wheels attached to the motor. This is the same as "engine braking" on a manual. The wheels turn the motor, which steals kinetic energy from the car and charges the battery.

There's no extra bits or anything. It's all in the drivetrain that's there already.