And if you do want to try it, I've found this kind of solar panel that works really well. It is designed to rechard deer feeders. The key thing that makes it work better than any other I have used is that the surface is covered in honeycomb shaped bumps. I think they are supposed to either focus the light onto the cells better (or it bends the light that comes from an angle to focus it onto the cells like the ends of some fiberoptic cables) because it will still put out a fair number of amps from almost any angle.They come in 12 volt but I used a 6 volt charger to run an MP3 player with a bad battery when I was out in the kayak. I just put each pole of the alligator clips to the correct poles on a 12 volt cell phone car charger that fit into the music player. Still used regular headphones but I put them in a little box where they would amplify like an old fashioned megaphone. So I basically made 100% green stereo system. I might buy a rechargeable 6 volt battery this summer so I dont have to worry about shady spots killing the MP3 player.
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If you have one of those bed covers you could put a bunch on there. On a sunny day that might be able to generate enough to make a difference. The intial cost of the panels will be what get you though. I think they were around $20-$25 each.