Running in your motor.. Put it in the car and run it for a practice run .. The brushes will be seated and the motor will be run in with a load on it . which to me is better ... power supply is the best way to run your charger . but If your using a car battery get a deep cell marine battery . you should be able to run all day with out it loosing too much charge to run your charger ... Batteries .. cycle them once .. 30amp discharge then equalize them before you charge them up to race ... good luck and have fun at the races..