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eyacht avatar image
eyacht asked

Why am I seeing panel voltage on the MPPT when the panels are covered?

Hi everyone ... I thought that when I put a tarp over the panels and some weights to hold it in place that I would not measure any PV at the MPPT, however, it's still almost full strength. Am I misunderstanding PV here or is there potentially something wrong? TYIA!

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2 Answers
bradleyh avatar image
bradleyh answered ·

Without a load it takes surprisingly little light to get a voltage on the panel. Are you measuring the voltage open circuit, or is the voltage being measured by the MPPT? Maybe your tarp isn't opaque enough. You could check the charge current with the tarp on and the system hooked up. You'll probably see a low, but non-zero charging current if the tarp is just letting too much light through. Check the voltage at night and see if it's much lower as you would expect.

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eyacht avatar image eyacht commented ·
thanks @bradleyh ... the tarp is a thick canvas one so i think it should be opaque enough. I'm measuring voltage at the MPPT across the PV terminals. I have normal load on the system. I'll measure the voltage after sunset and see what that says ...
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mvas avatar image
mvas answered ·

Disconnect the wires and measure the voltage on the PV and also the MPPT terminals. Open Circuit Voltage with essentially 0 amps is not "full strength". As soon as you apply a load to the PV wire, then you will see the voltage drop towards zero volts.

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eyacht avatar image eyacht commented ·
thanks @mvas ... I am measuring the voltage across the PV terminals on the MPPT ... is there another way to do it? I have a normal daily load on the system and I thought if I covered the panels then voltage should drop significantly but it's not.
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kevgermany avatar image kevgermany ♦♦ eyacht commented ·
The MPPT will maintain panel voltage to optimise output. Even if it very low.

Do not disconnect the panels while you have voltage. It will cause arcing, damage connections.


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