Generators = put in rotational movement to get power
You already have the heaviest parts on the ebike - motor and battery, just need some capacitors and charging circuit board which are light and not too big.
Cheap electric bikes I’ve ridden with regen breaking slow you down quite a bit.
Motors are generators when run inversely:
Motors = put in power to get rotational movement
Generators = put in rotational movement to get power
You already have the heaviest parts on the ebike - motor and battery, just need some capacitors and charging circuit board which are light and not too big.
Cheap electric bikes I’ve ridden with regen breaking slow you down quite a bit.