I have a small travel trailer. I have set it up with (2) 6 volt batteries wired in series. When drydocking, after I drive to a destination we only use a few lights and the refrigerator. The batteries will remain charged for 5 days. Then I will charge with my Champion 300 Watt Inverter generator. The problem is even after charging for a few hours and the interior gauge saying Fully Charged, the batteries will only last about a half day and need charging again. I don't understand what may be happening. Any help would be greatly appreciated.