Well, that's the beautiful thing about regenerative braking: The "external force" required to slow down the car comes from the electric motor itself, from the c

Well, that's the beautiful thing about regenerative braking: The "external force" required to slow down the car comes from the electric motor itself, from the counter-torque of the motor acting as a generator to charge the battery. It's not lossless but it's far better than letting all the kinetic energy dissipate as heat.