If you are rrefering to the coach battery, the three leads are to the generator, to the main DC breaker feeding the load center, and to the relay that allows the sharing of the chassis battery.
Thanks Chuck! This info gives me cause, I'm planning tho move the battery to the other side ( in the coach step) which would require routing these wires across the underbelly. I'm planning to do this because my 12v 200amp lithium battery won't fit in the present location.
This would require adding an additional 6 ft or so to the wires.
If you are extending the wiring length that caries these high current loads, consider using the next larger (numerically lower) size wire... 4awg becomes 2awg, etc. Replace the wire end to end, not just splice on to existing.