Thanks, built a pack and ran the car on the 16 tooh pinion. My 13 was not hardened and is toast. The battery at the end of my five minute run was at about 13 volts and the hyperion did not like it. The charger would not charge the battery. Had to charge it as a four cell for about five minutes before the charger would let me charge it as a five cell. I have 13 tooth pinion on the way should be here on Monday.