Regenerative braking returns a charge to the battery whenever you command the board to slow down. Examples include braking to stop, braking whilst going down a hill or even braking whilst riding in reverse. Simply coasting, or riding with only the remote trigger engaged does not put any amount of charge back into the battery.
Long slow braking regenerates more energy than fast hard braking when coming to a stop in the same location. Coasting with the remote trigger released, however, is more efficient in conserving energy than frequently using regenerative braking. Push-kicking to start and then slowly engaging the throttle will also conserve more energy than accelerating from a full stop using only the motors.
