Pictured below is a standard Club Car OBC unit. There are a few different methods by which they mount it, however all of them achieve the same function.
Here is a photo of a Precedent OBC with the 6x8 volt battery configurations
The OBC is the brain unit of the PowerDrive charger. Your standard factory charger is NOT a smart charger. It is merely a conduit by which power in converted from 120VAC to 48VDC in order to charge your cart's battery bank. The main ground cable runs through the hole in the OBC and that is how it determines the state of charge in the batteries. When you plug in your charger, the OBC tells it whether or not it needs to come on and charge and when charging tells it how long and when to shut off. If you have replaced your charger with a newer model like a Lester Summit II unit you no longer need the OBC as that charger has it's own brain system built into it.
There are two possible methods for the average user to keep the OBC correctly
1) We leave off one lug and send it prefilled with solder ready to install after the user has routed the cable through the OBC. Once you have run the cable, you solder the lug on and complete the cable.
2) We can cut the ground cable into two separate cables and will send instructions for creating a "passthrough stud" that will create an attachment point on both sides of the OBC. This method requires you to grab a few small parts from a hardware store or the likes to assemble. The diagram below gives you a basic idea of what it will ultimately look like.