No, the RV is not new, it's a 93 Roadtrek but the RV battery is just about brand new. I was thinking it's possible the big ol' Dodge 360's alternator may be pushing out high voltage, and with the house battery being in new condition it may be a couple volts high.
On my older inverter (with the built in voltmeter) it was reading Incoming voltage at 15V before pegging out. I know a fully charged brand new car battery can fully charge up to about 14V.
Do most people not put inverters in RV's? It seems like a cheap and easy solution to a generator.