Das is a little confused about the Prius. Prius owners DON'T plug the car in or charge the batteries via a wall socket. The battery for the electric engine is charged as you drive the car via the gas engine as well as through braking. There is nothing to plug in - ever. Also, Toyota's warranty on the batteries is 10 year or 100,000 miles. Prius' have been on the road for 10 years (in Japan) and 7 or 8 here in the states and there are very few instances of customers needing to replace the batteries from what I've been able to learn.