Ok, before I get yelled at, I know I could have actually purchased one for about $30 more than what I spent for just the parts for this project. While the goal was to save some money (maybe), primarily I just wanted to build one. I'd never worked with solar cells before. I'm making a 50 watt to go along with my factory built 50 watt. This was more involved than I originally thought, but it has been fun to do. Got the cells on eBay - forty, 3x6, untabbed, plus all the tabbing/connector wiring strips and a tube of flux. Actually they sent like 45, as some were broken (I knew that in advance). Had a couple of yard sale picture frames with archival glass, and picked up a 39"x78" EVA film from eBay. I have a bunch of aluminum framing that I'll build the actual frames from and already had a 30 amp charge controller in addition to the 20 amp I already have in the camper. Total cost so far is $53.
I'm building the unit to consist of 2 panels, each having 18 cells, in series. The frames will be hinged so it closes together to be a little smaller, but opens up to full size. Finished panel 1 today and should have panel 2 done tomorrow. Did a power test after encapsulation in EVA and was happy with the results. 10.2v open, 3.1 amp under load (this is an 18 cell arrangement per panel, 36 cells total). So when the two are finished I should have an open voltage of about 20v and amperage capability of about 3 amp. That matches up very close to my factory built panel.
Neither of these are permanently mounted, they are portable with a 25' feed line to the trailer. Trying to decide whether I should link the two systems in parallel and run everything down a single feed line to 1 controller, or have each of the systems (factory built and my 2 panel build) feed independent controllers (don't have a MPPT) and then have those feed the battery in parallel. My concern is that my home-built (or perhaps the factory built) will underperform the other system and thus pull it down in efficiency. What do you folks think?
Oh, and Conch Fritter's new varnish should be done this weekend. Had to stop for a few days due to temps and wind.
dave