I purchased a 5W solar panel from Sparkfun, and after using it outside for about a week, these large white spots started showing up.

White spots on solar panel

Here's a closeup: enter image description here

The solar panel is not being back-fed thanks to an inline diode blocking any reverse current.

What is causing these white spots to form. Is the panel overheating when connected to the load? Is this a manufacturing defect?

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    \$\begingroup\$ They look like bubbles caused by delamination of the panel. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 22 '15 at 18:29
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    \$\begingroup\$ That would be my guess as well, can you push carefully on the glass and see if the bubble (temporarily) goes away or moves? \$\endgroup\$ – Arsenal Aug 22 '15 at 18:30
  • \$\begingroup\$ The white spots definitely bulge out, but pushing on them doesn't make them move. \$\endgroup\$ – TRISAbits Aug 22 '15 at 18:34
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    \$\begingroup\$ I'd talk to SparkFun about this. This definitely shouldn't happen. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 22 '15 at 18:36
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    \$\begingroup\$ The web page mentions hard board backing. To me this is not suitable for use outdoors use without further sealing as it absorbs moisture.. \$\endgroup\$ – Spoon Aug 23 '15 at 8:48

I have no idea, but I found this picture of PV cell delamination from a now-defunct website. I think it looks a little bit similar to your case, so it might be delamination of the cell. But you compare the picture to yours and be the judge if it seems similar or not.

If it is indeed delamination, then that is a manufacturing defect.

PS. If the website comes up again, this picture should probably be linked to the original page instead of being re-uploaded here.

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  • \$\begingroup\$ I have yet to find a picture similar to my situation, but I would have to agree that it's most likely delamination. Interesting side note: apparently delamination gets accelerated with damp-heat cycling, like hot sun right after an intense rainfall: fsec.ucf.edu/en/publications/pdf/FSEC-PF-426-01.pdf \$\endgroup\$ – TRISAbits Aug 22 '15 at 19:26
  • \$\begingroup\$ Confirmed to be manufacturing defect. \$\endgroup\$ – TRISAbits Aug 27 '15 at 15:37

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