Alternator not charging deep cycle battery

I had a 1 volt drop between the engine battery and the house battery with the engine running. This prevented the hous battery from fully charging on the road. It turned out there was half a volt lost in a connector under the vehicle where power was taken from the wiring cable heading to the hitch jack. Another half volt was lost in the battery disconnect switch at the door plus wires to and from it. I fixed the first with a soldered joint bypassing the connector (carefully sealed with heat shrink) and the other by connecting straight to the battery instead of going through the switch.