OBC? Isn't that for club car? I thought he had EZGO.
The reed switch can be seen in the thread below. When the charger is connected, the reed switch opens up so there is no V on the little wire going to the controller. So the controller knows not to go because it is plugged in. When the charger is unplugged from the cart, the reed switch closes and there is V on the little wire so the controller knows it is safe to go.
http://www.buggiesgonewild.com/elect...tml#post628945
Hopefully this shows you the piece you are missing. Sorry for the delayed reply.