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Old 04-15-2009, 11:26 PM   #14 (permalink)
NiHaoMike
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The correct way is to use a boost converter. However, not any common boost converter can be used as in a solar application, as it must attempt to regulate the *input* voltage as well as the output voltage. The reason is that solar panels are more or less current sources up to near their open circuit voltage. (Read about the photoelectric effect for more information, but the basic explanation is that the electrons knocked free by light have a certain velocity and therefore a certain amount of voltage difference they can overcome.) The boost converter should try to pull down the input voltage to the desired value as long as the output voltage is not too high. Use a potentiometer to set it to maximize efficiency. If the panel voltage is clamped too low, efficiency suffers as a lot of the electron energy is wasted. If it is let to go too high, the low energy electrons will not be able to make their way to your circuit. The optimum point is something like 13-18v for a 12v panel.
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