A few things to add to what I said above:
- You should put a fuse in the +48V line as close as possible to the battery.
- If you have an OBC, the -48V must go to the B- or the cart will not charge properly because the OBC will not know how much power has been taken from the batteries by the reducer.
- You can make a 4-wire reducer switch off with the key by adding a 48V relay. The wires from the key will switch the relay on (with a small amount of power) and the relay switches the reducer on and can carry the larger power that it needs.
- It is best to run your 12V wiring through a fuse box and negative buss to your 12V accessories. Then they are properly fused in case of a short.
- You always run your 12V negatives back to the reducer. NEVER use the cart chassis to "earth" the negatives as you would on a car or truck.