I don't have the problem, my coach came with an 85 watt solar panel and controller and PO installed 2 more 125 watt panels. This keeps my batteries up and allows extended boondocking if we monitor power consumption.
But I do know that there is parasitic draw so using the batteries disconnects is the only way to prevent battery drain.
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi