I dont think that was a good idea . Gearing scooter motors and attaching it all to wheels relaibly is a big big undertaking unless you have very extensive experience with gearing and low voltage dc motors (its unlikely ) It will be a lot more difficult than you think to get a rolling chassis. Id recomend at least one bot with blue wheels and drills, once you feel that you know people that can help you with the scooter motors and you have looked inside pinser (that uses scooter motors i think identical to the ebay ones), then sell or store the drill motors and begin replacing it with scooter motors. As for the batteries, 2 7.2 V nicads or a 12 V sla battery.