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What is the best way to drop 20vdc down to 12vdc?
Last summer I built a solar panel. It works very nicely except that the cells which were rated at .35 volts actually turn out about .5 volts. And the current is around 3A, so I wound up with a panel that puts out close to 20 volts instead of the 12 volts I was planning on. The most obvious answer is to remove a few cells, but the panel is sealed closed and the cells would be damaged if I tried to open it again.
I was thinking along the lines of just tossing a resistor (or set of resistors) in line, but where do you find a resistor that small that is rated for 60 watts?
2 Answers
- billrussell42Lv 79 years agoFavorite Answer
"that small" ? do you have space limitations? Any 60 watt resistor will be large. But that will waste a lot of power.
Why do you want 12 volts? If you want to charge a 12 volt battery, you need 15 volts or more. Plus solar cells have a high internal resistance so at 3 amps, I doubt that the output is 20 volts. Did you measure that, voltage with 3 amps load?
But if you actually do get 20 volts AT 3 amps, then you could use a DC-DC converter to reduce that. In theory that would yield 12 volts at 5 amps. Good charge controllers have a built in DC-DC converter.
- rogerLv 79 years ago
