Rewiring battery bank to charger/inverter, couple of ?'s

It is often harder to get a good low resistance connection to the frame than a good low resistance connection via copper wire (especially one that is still low resistance in a year or two), but if you look up the proper parts and techniques used, it is certainly possible.

Of course it is better yet to have the controller and inverter so close to the batteries that there is no advantage to using the frame as a conductor.

Jim