Hello, I just purchased an old RV with only 28,000 miles on it. I redid the interior a bit, had some repair work done. My question is regarding the 12v part of it. It has a converter which works great when plugged into shore power. I have concluded that the converter does not run the 12v. No inverter. You run the lights, etc. like water heater off of the batteries. There are no “house deep cycle” batteries but rather two engine batteries. One starts the engine. One runs an optional generator. Both power the 12v. However, the converter only recharges one of the batteries and it is NOT the start the engine one. How do I keep from discharging that battery? I had a Winnie Class A before this so this configuration is puzzling me. Any help would be appreciated.