The power output to the inside plugs is 4 to 6 volts when it should be 120 volts? You may be reading a floating or residual voltage. Make sure that the breakers on the generator are not tripped. Turn them completely off and then back on.
Also, does your coach have an automatic transfer switch to power the coach when the generator is running? Or do you have to plug the coach power cord into the generator output?
If it has a transfer swith, it may not be transfering.
The batteries have nothing to do with the 120 volt output, all they do is crank the generator to start it.
Amateur Radio Operator (KE5DFR)|Full-Time! - 2012 6.7L Ford Crew Cab Dually -2013 HitchHiker Champagne 38RLRSB - Travel with one Standard Schnauzer and one small Timneh African Gray Parrot