Are my solar panels EOL

XO4001 · Jan 9, 2022

Having 48 panels in 4 string’s of each 12.

All panels in the same plane.

The panels in front are the Chinese.

2 strings with Chinese 250 W panels 8years old.

2 strings with Peimar 300 W panels 4 years old.

Noticed that the Chinese panels is putting out real pour sometimes ¼ or ½ of the Peimar.

I expect that they would output 1/5 less but it is substantial more.

There are some snail trails on them but they suppose not the reason of less output.

Any ideas of what could be the reason or are they just End Of Live after 8 years.

sunshine_eggo · Jan 9, 2022

You need to test the Voc and Isc of each panel to answer this question. A single underperforming panel in a string will pull ALL panels in that string down to its level.

chrisski · Jan 9, 2022

That is a lot of panels to check. Would take me hours One by one. 12 panels in series is more thanI feel comfortable with checking with my $25 multimeter.

Since thermal imaging has come down a lot and affordable by normal people and not just the world’s largest governments, I wonder if FLIR imagining would help with that:

Inspecting solar panels with thermal imaging

Solar panels may develop defects that can be easily fixed if detected early enough. Many solar panel installers cooperate with experienced thermographers that offer regular thermal imaging inspections to ensure the safety and effective deployment of solar systems.

www.maintworld.com

XO4001 · Jan 9, 2022

sunshine_eggo said:
You need to test the Voc and Isc of each panel to answer this question. A single underperforming panel in a string will pull ALL panels in that string down to its level.

Thanks for your reply, just looked at how to test and will give this a try tomorrow if weather permitting.

XO4001 · Jan 9, 2022

chrisski said:
That is a lot of panels to check. Would take me hours One by one. 12 panels in series is more thanI feel comfortable with checking with my $25 multimeter.

Since thermal imaging has come down a lot and affordable by normal people and not just the world’s largest governments, I wonder if FLIR imagining would help with that:

Inspecting solar panels with thermal imaging

Solar panels may develop defects that can be easily fixed if detected early enough. Many solar panel installers cooperate with experienced thermographers that offer regular thermal imaging inspections to ensure the safety and effective deployment of solar systems.

www.maintworld.com

View attachment 78975

Thanks for the suggestion but I have no flir equipment in my toolkit, since the panels are ground mount I think it is not too troublesome to check them 1 by 1.

littleharbor2 · Jan 9, 2022

Do not disconnect any panels while the sun is shining. It would be very dangerous as well as it will destroy the connectors. You might be able to narrow down some problem panels/string with a DC clamp meter.
This is a grid tie system I presume?

XO4001 · Jan 9, 2022

littleharbor2 said:
Do not disconnect any panels while the sun is shining. It would be very dangerous as well as it will destroy the connectors. You might be able to narrow down some problem panels/string with a DC clamp meter.
This is a grid tie system I presume?

Thanks, Im aware of the danger working with high voltage DC.
Planning to take 1 string out production and disconnect all panels from each other to perform the testing and hopefully I find the bad one or more.
Can you tell me more how I can narrow it down with a clamp meter?
And yes it's grid tied with zero feedback and battery's connected

littleharbor2 · Jan 9, 2022

I would think, while the system is up and running you might be able to test each string for starters with your DC clamp meter. Looks like you know which string is bad though, correct?
Once you isolate that string you need to find out the bad panel(s) in that string. Short of dismounting the panels you should be able to do a short circuit current test on each panel with a multimeter. I have MC-4 connectors with short lengths of PV wire still connected that I push the test lead points into to make it easy to connect to each panel. I have clipped off the parts of the connectors that lock together, making it easier to test multiple panels at a time. If you don't find a problem this way then you need to put a load inline with the test leads. Sometimes a short circuit test isn't enough to reveal problems without some kind of load.

XO4001 · Jan 9, 2022

littleharbor2 said:
I would think, while the system is up and running you might be able to test each string for starters with your DC clamp meter. Looks like you know which string is bad though, correct?

Yes I know exactly which is producing less, just changed 2 photos in my first post that were not correct.
Have to wait a couple days for testing because rain is expected coming days.

littleharbor2 · Jan 9, 2022

I'm going to guess by the voltage of the good panels that you have strings of 8 panels x3 per side, correct?
Hard to tell by the current but if you DO have 3 strings per side your current is low. Is this because you have zero backfeed and relatively full batteries? If there's nothing to consume power your system has to throttle back. Do you have any large loads you can turn on to see what happens to the incoming power?

XO4001 · Jan 9, 2022

No i'm having strings of 12 panels and 4 strings on 2 pc 5kW Deye inverters ( each inverter has 1 string good and 1 bad) batteries are 50% ( 4pc 16s 277ah) so basically i can use all i generate.

littleharbor2 · Jan 9, 2022

XO4001 said:
No i'm having strings of 12 panels and 4 strings on 2 pc 5kW Deye inverters ( each inverter has 1 string good and 1 bad) batteries are 50% ( 4pc 16s 277ah) so basically i can use all i generate.

OK I see those are 60 cell panels. Without counting I assumed they are 72 cell , which have higher voltage. Still less than 30 volts from 300 watt panels is pretty low. The lowest voltage string is only averaging 14 volts per panel. So you must have some panels putting out no voltage

XO4001 · Jan 9, 2022

littleharbor2 said:
So you must have some panels putting out no voltage

If that's the case it would easy to find.
Thanks for all the responses.

littleharbor2 · Jan 9, 2022

Well, thing is they can put out somewhat normal open circuit voltage even if compromised. That's where putting them under load helps find the tricky ones.

XO4001 · Jan 9, 2022

Would a couple of incandescent light bulbs in parallel do the trick as a load?
Say 2 100W 115VAC bulbs at midday sun maybe I can find some in a store.
Or a halogen bulb.

littleharbor2 · Jan 9, 2022

Not sure if ac bulbs work with dc and a halogen or 200 watts of incandesent bulbs is too much load. A automotive headlight would work I understand. I have a gadget made with MC-4 fittings and a piece of Nichrome wire coil ( heater coil) that I use. If it gets screaming hot right away I know the panel passes the load test.

Bvillebob · Jan 9, 2022

A DC clamp ammeter is what you need. I have 40 panels, after installing them I checked them and found 2 that weren't producing, turned out to be due to bad MC4 connections which were easily fixed. Quick and easy to diagnose. You can get one for about $30 these days, just be careful it reads DC amps, many of the cheaper ones are AC amps only.

Bud Martin · Jan 9, 2022

100W 120V incandescent will have Cold resistance of about 10 Ohms (hot resistance is higher, it is about 144 Ohms), you can check it with Ohm meter.
You should get DC Clamp-on meter as suggested, it is a great tool to have.

XO4001 · Jan 10, 2022

I have a DC clamp meter but was thinking that when you make a full short without resistor it will not give the correct reading in reference to voltage because that will collapse.
Do you not have to read both voltage and amps at the same time to find the condition of the panel?

littleharbor2 · Jan 10, 2022

My thinking is If the panel will support an applied load it is fine. Of course it should be a reasonable load. Too small and it could still work, too large and it may not work.

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