Solar panels come in all kinds of sizes, and also different voltages. You need the right application for the job you want to do.
If the voltage is between 19 and 22 volts "Open Circuit" then it is considered a 12 volt nominal panel, and can be used with a low cost Pulse Width Modulation (PMW) solar controller, I bought a 10 amp one for $13. To use a higher voltage panel in a 12 volt application, it would require the more expensive MPPT controller. Maximum Power Point Tracking is something that came out around 1996, where the solar panel's maximum voltage is used to charge the battery, while the controller is used to convert the 19 volts to 13 volts at a higher amperage. So 10 amps at 19 volts can be converted to 13 amps at 13 volts.
Today, MPPT controllers can take in 40 volts and put out the desired voltage output, even if set up for 12 or 24 volt battery. And some models can take in as many as 150 volts - so the solar panels can be wired in a string, for the minimal voltage loss, and then wired to the controller that way.
Yet I would not recommend sting wiring for a RV solar system. The problem is that if there is a small shadow on one panel, it can reduce the maximum potential amperage of all the panels in that string. And you know how RV's like to be under trees sometimes. In a house, that is normally not a problem.
SunElec.com - link above, has 12 volt panels, PWM and MPPT controllers. They also sell a lot of home based systems, with 39+ volt open circuit ratings, so the ones over 22 volts would require a MPPT controller.
Fred.
Money can't buy happiness but somehow it's more comfortable to cry in a
Porsche or Country Coach!
If there's a WILL, I want to be in it!
I havn't been everywhere, but it's on my list.
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