Burnt spots at the panels

[Takis]

Hello friends,

Today I've discovered some burnt spots on 3 out of 4 solar panels like the same as reported at the 1st post on https://www.solarpaneltalk.com/forum...-strange-spots
All are located at the same place of some cells.
One panel of them which has no spots is from different batch. All are Canadian solar 330w
wiring is 2 series pairs in parallel.

Probably I haven't spot them at the first place, but could be produced by my mistake?
1. Sometimes I push panels to the limits by drawing all amps.
2. Sometimes I switch on off panels while the sun is shinning full.
3. Recently I ve found out a weak connection that leads to high voltage drop.

Maybe those burn spots are came from factory but I need your opinion as well.

Thanks in advance.

[Mike90250]

There should be nothing a user can do, that would cause those spots. They were either there from factory or developed shortly afterward. What does the plastic backsheet look like in that area ? is it fine, or scorched ?

If it's fine, you likely got some bad looking cells from the factory. If the backsheet is damaged, file a warranty claim ASAP, as the panels are no longer sealed and there is a defect

It's such a small spot, it should not have much effect on harvest, but if they grow, file a warranty claim

[Takis]

The back side of panel has no black spots or any kind of damage. The front side has no breaks, silicone is fine no dust at the cells. Seems that panels are fine.

I will have an eye on them if those burnt spots get bigger. Though seems that is a pattern on their location. Bottom and center of some cells.

Thanks

[bob-n]

FLIR has a guide for using thermal cameras (link below). Starting on page 32 (image capture below is from this guide), they mention that a thermal camera can be used to find a bad cell or defect in a PV panel.
FLIR_PV_Photos.jpg

http://www.flirmedia.com/MMC/THG/Brochures/T820325/T820325_EN.pdf

Thermal cameras are getting cheaper and better. If you can find a friend with a thermal camera, take a picture of your panel during normal operation and it shows a temerature difference around one cell, that clearly tells you that one cell is damaged or obstructed. If it appears thermally uniform, then perhaps the damage or defect is simply cosmetic or not yet significant.

I'd love to hear from others that have experimented with thermal pictures of PV panels.

[Takis]

Bob thanks.

The right image shows physical damage I suppose by the welding machine. All at the same location.

How is it possible for an inspector not to see them ?

[azdave]

Bob thanks.

The right image shows physical damage I suppose by the welding machine. All at the same location.

How is it possible for an inspector not to see them ?

Human error or not looking for them that closely to begin with?

When you have hundreds of identical items to inspect visually a human can only do so much. We installed machine vision cameras on final inspection processes at work and while defects have not decreased much the number that make past final QC has fallen to less than 1 per million.

[bob-n]

In the right photo, I think that the four glowing spots on the right center of the panels are the junction boxes. Is that what you mean? If so, they are slightly hotter than the rest of the panel because all of the current necks through joints there. That's not an issue and that's not what the author was highlighting.

Again in the right photo, the center shows a bigger, hotter spot. That's what the author is highlighting. We have no idea if this was obvious with ordinary visible light but it seems to be higher temperature in that one cell. It could be microscopic or otherwise invisible point damage in that cell causing leakage, resulting in the power generated by that cell being dissipated right there, rather than being supplied to the inverter.

Often, authors of technical sales documents spend months searching for the best image to highlight their point. We are to assume that this was an actual event that the thermal camera detected and was otherwise missed. If you're cynnical, however...

[Takis]

Not cynical. Maybe I'm having in my mind a pattern for the welding spots and the eye follows that pattern.
to be honest I haven't noticed the spot on the center.