2 panels 2 different sets of readings

Purchased a 2 panel kit and am reading in full sun in Pennsylvania at real noon, 20.8 volts on one panel but only 19.8 on another panel. O noticed dents , more so on the weaker panel, on the back white Teflon coating. I was surprised to see this as this will surely have caused some micro fractures in the cells I would assume. Have others had a similar experience?
  • Hello Scott,

    Are you describing an open circuit voltage test? The panel readings will differ from the specification sheet depending on location, temperature, insolation, air mass to name a few factors.  Have you tried connecting your panels under load to see their performance? Which panel are you referring to? 

  • I purchased the two panel mono kit. The two panels were side by side during the test. I'm referring to an open circuit voltage test. One tests higher than the other and neither reach peak which is ok because it is still early spring and in Pennsylvania so to be expected. I'm more worried about why one panel is lower as it seems to have some dings on the back of the panel. Having worked in the industry many years ago I'd imagine this will cause microfractures and thus cause a decrease of overall panel effectiveness
  • Scout, remember panels don't operate at their open circuit voltage. With a PWM controller they operate @ just over battery voltage. MPPT forces panels to operate at their max power pt.

    If one looks at the IV curve of say a 100 w mono panel, specs with show this

    look at the bottom of this RNG-100 specs sheet

    Note the IV curve, this is lab conditions with a cool panel, lots of light perpendicular to the panel ...

    Not the IV curve shows constant current at voltages below ~15 and tapers off to zero @ OCV.

    If you were to recreate this curve at different amounts of light, temperature ect you'll get far different results.

    I would not be too worried about the 1v difference you experience in OCV.

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