My trailer will be parked in a covered area but I planned to have the solar panel immediately outside facing south. We're in San Diego so we get plenty of sun. The battery will most likely be partially depleted just prior to storage. I was hoping to set up the solar panel, etc. and leave it hooked up until the next trailer use, about a month later. Is that the "sweet deal" scenario you mentioned? If so, I think Harry hit the sweet spot with the BatteryMinder controller and 15W panel suggestion.
What I was trying to say there was that having two chargers on your trailer at the same time, one standard plug-in battery
charger or trailer converter, plus a BatteryMinder charger/desulfation unit won't work. If you use a BatteryMinder it has to be the only charger on the system. So, assuming you don't "plug in" when you store your trailer, the solar
BatteryMinder would work just fine for you.
BatteryMinder sells two Solar
Controller/Solar Panel combos. Both have the same 15 Amp (180 watt) BatteryMinder charge controller and either a 5 or 15w amorphous (low efficiency) solar panel
. They cost $110 and $150, respectively.
Since the Battery
Minder itself runs about $100, that means for $10 you'd get a 5-watt panel (about $2/watt), which is a pretty good price; the 15-watt panel adds $50 (about $3.30/watt), which is about average pricing for a panel on a per-watt basis these days.
If I were installing my solar
system from scratch today I might buy the package with the cute little 5-watt panel and install it on the frame extension where my 5th-wheel's hitch is. That makes sense for me because, when I park the trailer, the hitch faces south and outward from under the roof it's parked under. It'd get enough sunlight to keep the battery desulfated and fully charged.
I would not get the $150 kit. My reasoning is, if I'm going to have big panels I want them to be big, cheap efficient
panels, and for the same physical size as the BatteryMinder 15-watt panel I can buy a 30-watt panel that'll last longer under the sun for around $100. Better yet, buy a pair of 50-watt panels for about $175 each. A 100-watt solar system can keep my trailer lit, my water pump pumping, my furnace
furnacing, and my little 12v, 10.2" AM/FM/DVD/LCD TV wasting my brains away all summer long without electric hookups.