That makes it even easier, when you are changing things over to accommodate the new set up (6-6s) to get something wrong. As you look at the battery pack you will see some heavy wires (probably 6 gauge). These wires do two things. Five of them connect the batteries in a series con figuration going from – to +, - to +, - to +, - to +, - to +. The first – is called B- and the top + is the B+. They should add up to around 38 volts. But there are two more that take off and go to the motor and its reversing and speed control circuitry. That’s the two I’m suspicious of. They must come off of B- and B+, not from anywhere else in the series string. Only B+ and B- will have two of the heavy wires on each of them.