Storing camper and want to keep batteries charged....solar?

I use a 30-watt Renogy solar panel and a Battery Minder charge controller. The panel is about 18-inches square. I zip tie the panel to the top of my rear ladder, pointing it in the proper direction and elevation to get the most winter sun.

I run a power line down the ladder and under the 5th-wheel to the charge controller which is next to my batteries in the front storage compartment. Keeps my 4 6-volt batteries topped off.