I have one I pulled from one of those stick in the ground lights. It is 6 inches by 8 inches and I have bolted it to the front rack. It produces 6 volts in the shade and 9 volts in the sun. I hooked it directly to a white LED and left it on for 8 hours this should have fried the LED but did not. Batteries make very good voltage regulators if you hook a solar cell to 4 NiMh batteries and run a cord from it should not produce more than 5.6 volts ideal for charging anything that runs on a USB cord. The thing is not to get greedy when using rigged power if you need to charge a phone give it only the charge you need to complete the call.