I think I have a good solar system for my uses. Two 100 watt renogy solar panels on the roof, two 220 amp Crown six volt batteries and a 40 amp mppt controller. When I have been out for two or three days and nights running on just solar I do fine. What I don't under stand is when my batteries get down to about 12.3 or 12.4 because of cloudy days and rain and I plug in to electric they come up to 12.6 and stay. If it is real sunny I un plug and immediately the meter goes to 14.2 for a bit topping off my charge. What I am wondering is why doesn't it go ahead and charge like this with it plugged in? It is still on solar when plugged in.