How to Power Your enclosed Trailer for free 

Having done things like this for some time.... ditch the inverter. Replace it with a 12V SLA battery (as many as you want - just parallel them). Then run 12V lighting. Now you can use your lights 24/7! Not just when the sun is up.

The lack of panel wattage and the minimal battery storage is clearly highly limiting, but having something is better than having nothing and you definitely have something here. You did really well given how little money you spent on the system. I'll ditto DrFiero's comment nearby. For building a system on the cheap (we'll assume you can't afford LiFePO4)... so then SLA is what you should go with. You don't want wet-cell lead-acid inside your trailer, that's a bit dangerous actually. It would also be a good idea to have a main battery fuse. Once you can swing it, adding a bit more solar and a bit more battery storage will solve the time / duration limitations you are hitting up against. You have only a single 20W panel on the roof there and I'm impressed that you are getting so much out of it but... oh man that's really a tiny little solar panel. A quick little expansion would be to get a 50W, 70W, or 75W solar panel instead of that 20W. Or even get the second panel and parallel it with the 20W. -Matt

is as long as the sun is out the light works put in a sun roof get rid of the middle man