yep that battery pack was wired in backwards. if you are going to up the voltage then up the controller also. I moded my Panterra fusion with a 1500 watt 48-72 voltage controller and I bought form ESP some wiring connectors and a throttle THR-122. the throttle has a 3 speed control switch at low speed I can cruise at 20mph all day and at high speed it can cruise at 30mph easy. but I have hills around my house and high speed allows me to climb them good. the only down fall is that the motor heats up at high speed since it is still 750 watts so I limit high speed to climbing hills only. medium gets me 25mph too but you limit yourself to the laws of the state you live in and the cops won't mess with you much. Now I have not wired in any extra batteries yet but I let you know what happens then.