This is how the wiring look inside the prefab. I made it this way so that I could dismantle it easily when I need to remove the charging unit.
Top right is the voltage regulator. White switch is just an ordinary house light switch. The black lamp on the left is my back-up lamp that originally came from a Mitsubishi Pajero. It is 12 volts and have cigarette lighter socket. All the electrical wires came from scrap.