Buying used panels... What is a proper way to test the entire panel

[TheeBigGuy]

I bought a couple used panels cheap!!.. With a clamp amp meter they tested late in the day about 20% below spec... How should they be tested to make sure all cells are working?

 

[jasonhc73]

Plug the DC Voltmeter directly into the ends on the panel. Aim the panel as best you can to a right angle to the sun, as close to high noon as you can get.

This will give you the VOC at that particular time and date. If the number showing is within 10~15% of the rated panel, you are good to go. Temperature also makes a big difference.

"Standard Conditions" are 1000 w/m2 lux and 25°C. The colder the higher the volts, the hotter the lower the volts.


Don't look at the sun! Make a quadrant (print the file and get a straw+string, or read the instructions and use a straw)

 

[TheeBigGuy]

Plug the DC Voltmeter directly into the ends on the panel. Aim the panel as best you can to a right angle to the sun, as close to high noon as you can get.

This will give you the VOC at that particular time and date. If the number showing is within 10~15% of the rated panel, you are good to go. Temperature also makes a big difference.

"Standard Conditions" are 1000 w/m2 lux and 25°C. The colder the higher the volts, the hotter the lower the volts.
View attachment 6127 View attachment 6128

Don't look at the sun! Make a quadrant (print the file and get a straw+string, or read the instructions and use a straw)
[/QUOTE
Thank you... I guess I need to restate my question..I bought used panels and one of them ended up peaking at 6.7amps.. 365 watt 9.2 amp panel...After putting it on a load one section of the panel is not working... Is there a way to test each section of a used panel so I don't make the same mistake? thanks

 

[SCClockDr]

No, unless you separate the glass. Next time bring a load with your meter. If you plan to do this many times, build a metered load with solar MC4 plugs (remove the locking part).

 

[Supervstech]

Actually, you can...
But you need an infrared camera...

power the panel, and look at each cell, they should glow equally...

 

[jasonhc73]

Actually, you can...
But you need an infrared camera...

power the panel, and look at each cell, they should glow equally...

Good idea.

What's a good source for one? I have seen one that connects to a phone. But, still seems pretty high dollar.

 

[Supervstech]

I use the phone one works great.

 

[TheeBigGuy]

I use the phone one works great.

A phone that shoots infrared or an app that simulates infrared.. If so what app worked for you?..thanks

 

[DThames]

I will repeat someone's previous tip to point the panel at the sun, put a 3D block (like short piece of 2x4) on the panel and aim the panel so there is no shadow on any side of the block. Great trick for good aim.

 

[MrNatural22]

I will repeat someone's previous tip to point the panel at the sun, put a 3D block (like short piece of 2x4) on the panel and aim the panel so there is no shadow on any side of the block. Great trick for good aim.

Or even a small short plunger with wooden dowel stuck to the middle of the panel pointed til no shadow as mentioned in many aiming posts here over time. ?

 

[KBWaldron]

Don't forget to also open the j-box and check the diodes. Preferably if your multimeter has a diode checker. I picked up 8 six-year old panels recently. Of these, only one was without at least one faulty diode. Interestingly there was little variance in performance when I tested them. But that would make sense as the diodes only participate when there is shading.
I've ordered diodes and will be replacing all the diodes. I figure the other ones are only a short time away from dying as well.
At first I had thought to put more than one diode on each string in parallel, but I'm concerned that while that reduces the load on each diode it's just more diodes to go bad. I figure I'll just test them every 6 months or so.

 

[jasonhc73]

Or even a small short plunger with wooden dowel stuck to the middle of the panel pointed til no shadow as mentioned in many aiming posts here over time. ?

After "checking" a shadow. By far the quickest and easiest way to cast a shadow to get the "noon" angle, is with a tool you can't loose or forget.

Just put your finger anywhere flat on the panel. If you see any shadow, then the angle is not perfect. You don't have to be anywhere near exact. STC is only 1.5 ATM, which is anywhere around 11 to 1 on the noon clock.