Your choice of PWM versus MPPT solar charge controllers is critical if you choose high voltage grid-tie solar panels for your RV. I have flexible grid-tie Unisolar panels on my RV and I upgraded to MPPT. Watch the video to learn why.
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MPPT charge controllers operate more efficiently than PWM controllers, can be used with higher voltage panels, and are able to convert unused voltage to higher amperage. My panels output a higher voltage than standard RV solar panels. For this reason I needed to install a quality MPPT controller to take advantage of the higher voltage.
A PWM controller can also be used with higher voltage panels (20 volts and higher) as long as the voltage does not exceed the maximum input voltage of the controller. However, only a portion of the power from a high voltage solar array will pass through a PWM controller to your battery bank. So, if you have high voltage panels, an MPPT controller is recommended.