The Power Regulator board has connections to three 12 volt batteries. Two batteries were for the two drive motors and one was for the electronics. The logic battery went to a switching power regulator that supplied regulated 5 volts DC and unregulated 12 volts DC. The board also has a 28 volt DC input from the external power station  to recharge the batteries.

Here is the schematic for this board.

Here is a picture of the complete printed circuit board.