I purchased a vehicle a few months ago with a dual battery system installed. Both batteries were charged in the 12.5 volt range. Over time, the secondary battery has lost it's charge. I don't drive a lot and suspect this may be the culprit, but not sure. I have taken a couple of long trips since I purchased her, and it seems to rectify itself. I doubt that it is good for the battery to sit with a low charge for weeks at a time, so should I look at some sort of battery maintenance device to keep them both topped off while not on the road? Thanks for your input.