I have 2 sets of batteries on my 30ft. sailboat. 2 for the engine and running lights and 2 for radio, tape deck,bilge,etc. both independent of each other with their own battery switch. Yesterday, I decided to use position "2" for the radio since I normally run position "1" all the time and didn't get anything to come on from that panel. When I checked both batteries, they read "fully charged". I then went back to position "1" and everything worked fine. Are my cables hooked up wrong or is there another reason for this?