My trailer power system does a very good job of trickle charging as needed. In 9 months of use, I have had the trailer connected to AC when not traveling (we camp where there are hookups) and fluid levels remain correct and the batteries (2 of them) seem to be fine. According to my dealer's service manager (he seems to really know what he is talking about), my TT has a charging controller like the Battery Tender. I use a Battery Tender on my generator battery. It is always connected.