I got up to 17 volts in the sunlight, very nice. Edit: I added a LM2596 buck module (small PCB, a few bucks) to the output, now when the Sunforce outputs at least 10.5V, the LM2596 outputs 14V. When the Sunforce is running on 17V the output is still 14V. This is controlled by a small potentiometer on the board. I don't think 14V will hurt the battery, but it's definitely enough to keep it charged. I made another one for my other car and one for a friend. It's good when it's very cold outside and there are no problems with the starter! The battery remains charged.
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