Please see my post dated 7/21/2012 regarding a similar issue with my 2003 Terry Dakota TT. What I discovered in my case was that the Power Converter had come unplugged and the 12v system was working strictly from the battery and the battery was not charging. Once I plugged the WFCO power converter back in, everything worked fine. For what it's worth, the battery should charge from your tow vehicle while you are towing and from the Power Converter when you are plugged into 120V power. My trailer has a separate Power Dynamics Power Center that consists of (5) breakers and 12 automotive fuses. The breakers are on the left and are for the 120v side while the automotive fuses are on the right and handle the 12v side of things. When you are plugged into 120v, if everything is working correctly, you should not need your battery at all. I don't have a switch similar to what you are talking about, but I do have a battery disconnect at the battery which is nothing more than a knife-type switch that disconnects the battery altogether. I never disconnect anything, simply plug-in 120v power cord and go from there.