 Check out this Solar Stella project, it is a Solar powered Instrument Amplifier from Crazy but Able. This project is based around the $35 Stalla Amp but has been modified to operate using a solar panel. There are quite a few extra features built into the project that you would normally not see in DIY projects such as thermal battery monitoring for safety. Since the Stella works down to 3 volts it is a perfect candidate for a solar implant.
 “My original plan for this amp was to make a rather rugged poly-coated wood enclosure that could stand up to being left outside in a light rain. On the other hand, I also wanted to finish my amp by the time that the Minne Maker Faire rolled around. I quickly realized that my woodworking skills were not up to the task of being able to make an amplifier enclosure with the time that I had.
I started looking at what cigar boxes I had on hand. I considered a number of them, but ultimately decided on a Romeo and Julieta box that I picked up at a thrift store. It was a hard choice, because this particular box has some very beautiful cover art on the lid (inside and out), and I would have to cover it up with the solar panel. I decided to cover it up with the solar panel anyway, because I could see the original artwork when I opened up the lid.”
