You may have a bad converter/charger. There are several threads on the topic. Check them out for some helpful information. Also check the two reverse current fuses in your power panel. They are off by themselves to the left over by the AC breakers. WFCO has a diagnostic check list that is very helpful in determining whether your converter/charger is bad. You can find replacements on Amazon and they're pretty easy to install yourself, if you understand the basics of a 12v system. People have arguments about whether one brand is better than another. The thing you want to make sure about is that the new one will fit the power distribution box.
We just replaced a 9 year old WFCO charger with a new one of the same brand. I followed the advice of one member and put in a little cushioning of foam rubber below the unit to dampen vibrations. So far, it's working fine. It has a 2 year warranty. Others on the board say WFCO is of poor quality and prefer another brand, the name of which I don't recall at the moment, but I don't think there has been any objective studies proving one better than the other; just anecdotal experiences. Some people say Fords are better, while others like Dodges. Me, I like a good tequila,