Hello Mac, to keep my battery up when stored I was using a
50 watt solar panel mounted to the back of my trailer with an
MPPT solar charger initially and it worked great until winter hit and the sun wasn't shinning directly on it anymore where its parked (some days the battery voltage wouldn't show fully charged, but it was close to it). I then added a
100 watt panel on the roof where the sun always hits and
a second MPPT solar charger and it keeps the battery charged 100% (105 amp hour flooded deep cycle battery). With the
150 watts of solar I can run my
Dometic 12v Fridge on Performance at the
coldest settings while driving down the road and it keeps my battery fully charged even after driving for 8-10 hours (of course the TV charges it a little too while towing through the 7 pin connector). So I agree with Kevin,
100 watts will be
plenty to maintain it for storage. The max I have seen being ouputted from the
100 watt panel by the controller was around
6 amps (when I am running the fridge and lights, or what not) and the max from the
50 watt panel was around
2.5 amps. When no appliances are on the solar chargers just maintain the battery with
.1 to .2 amps most of the time when I walk by and check it. Below are links to the panels and MPPT Chargers I purchased and I have been using them for a year or so, of course they were cheaper when I bought them, the prices have gone up some. Note the 50 watt panel comes with the MPPT charger, but I cut the wire alligator clips off and soldered in some ring terminals I could bolt down to the battery in place of them.
Solar Panel 100 Watt
MPPT solar charger (has 3 different modes, one for Flooded, AGM, and Lithium)
Solar Panel 50 Watt w/MPPT solar charger
