PHOTO CREDITS: Retrokit Want to ride a battery bike… and you also want a vintage Vespa? Retrokit can help you with that, and it looks like a fairly simple process. There are two main parts to the Retrokit system—a 7,000 watt motor that installs at the back of the scooter, and a 2,350 watt-hour battery pack. That li-ion battery pack is removable, and takes about four hours to charge.