[cymbeline]

“current flows through the circuit into the battery.”

Isn’t that saying that some of the momentum energy charges the batteries?

[GingisK]

Why, of course. But that is not 100% efficient. Energy is wasted through the heating of the electrical system and eventually the mechanical brakes. Bear in mind that there are also energy losses as the car is pushed through the air.

Perpetual motion doesn't happen in the real world. Energy conversion will never occur without waste. Anything that results in heat dissipation removes the energy from the system. It is no longer available for transfer back to the battery.

[GingisK]

Maybe this will help: Regenerative Braking