Chris, sounds like you have a couple things going on. With your engine running both chassis and house batteries should be charging, neither are so I believe you alternator is not working. Then you start the generator and both batteries start to charge. I believe you battery boost switch is turned on. That switch may be called emergency start switch, it ties together both batteries and that would be why your gauge on the dash for the chassis battery starts showing a charge. Get you multi meter tester out and check charge levels at both sides of the solenoid, both batteries, if you have a battery isolator check there too. 12.6 battery is fully charged but not being charged by the alternator, 13.6 or so, alternator is charging battery, 12.3, that you showed is about 40% charged, in the 11's, it's dead. Good luck!