Frank, we usually are camped at locations with no hookups -- we can go 10 days without the batteries totally dieing-out on us but that's mostly due to us being really conservative. The solar panel is 65 watts and certainly helps, but the biggest power draw we typically have is the water pump and probably the furnace blower. If we were running stereo, television and other such appliances I'm sure the solar panel wouldn't be a heck of a lot of help. The solar sure does help slow the loses though! We do have a controller for the panel. It's not a super expensive model or anything -- I don't think it's really as important an item when using such a low powered system as ours. Overcharging is not usually an issue.