Got 13 year old panels and don't know where the power is going to

[keepsake]

Got 230 watt panels from 2012. 44 of them. 4 strings of 11 each.
Each string open circuit is 350 volts within 5 volts. When loaded into the inverter I measure only 11 amps from TWO STRINGS.
So with ample sunlight two strings give me at most 2700 watts. Each string is about 6.5 amps.
Math says 230 watts time 22 should be more like 5000 watts.
Same for the other inverter and same structure.
So essential identical characteristics.

Should I suspect one panel in each string is crippled ?
As in in-panel cells that are open circuit.
If there are 6 rows of 10 cells in each panel, it would only take one or two to restrict the current flow.
How does one easily find that panel ?
At age 70 I don't want to metering each panel on a roof.
Would a temp gun detect anything usable with a scan of the live panel ?
A clamp on meter is useless to find the bottle neck panel.

Thoughts ?

 

[keepsake]

Original system was 10 kw. Feeding into two 5 kw grid tie units.

 

[wpns]

Can you measure the Isc of the individual strings?

Just hook up one at a time into the inverter and see what you get for Vmp and Imp?

Give us more details on your panels, arrays, wiring, orientation, etc and we might be able to see a problem. Pictures are particularly useful.

 

[keepsake]

44 Powertec Plus 230/6PH Panels
10.2 kw PV system
Fronius IG5100 Inverter

What is LSC

What is LSC (loss of service continuity category) | Schneider Electric UK​

https://www.se.com/uk/en/faqs/FA402...oss of,the consequences on the installation.#
I have open circuit measurements of 348,349,345,342 volts
And currents are 6 amps each under load at 230 volts
What I cannot easily get is the individual panel stats
It's just strange that all 4 strings are acting the same in this way under power scenario.

 

[wpns]

44 Powertec Plus 230/6PH Panels
10.2 kw PV system
Fronius IG5100 Inverter

What is LSC

What is LSC (loss of service continuity category) | Schneider Electric UK​

https://www.se.com/uk/en/faqs/FA402828/#:~:text=LSC stands for: Loss of,the consequences on the installation.#
I have open circuit measurements of 348,349,345,342 volts
And currents are 6 amps each under load at 230 volts
What I cannot easily get is the individual panel stats
It's just strange that all 4 strings are acting the same in this way under power scenario.

I get that, but we don’t know how (or even in what country) your arrays are mounted, or anything else about your system. Can you post pictures?

Did it ever work “properly“? 13 years is maybe half your expected lifetime…

 

[keepsake]

I think the name is more: MAGE / Powertec

My question is more of a generic nature. Can panels, over time, lose one of their cell chains and under produce for just that reason? iow. The panel is not 'dead' and not just old, but more like one of the six cell paths is open. Does this Powertec have a history of this ?

 

[740GLE]

44 Powertec Plus 230/6PH Panels
10.2 kw PV system
Fronius IG5100 Inverter

What is LSC

What is LSC (loss of service continuity category) | Schneider Electric UK​

https://www.se.com/uk/en/faqs/FA402828/#:~:text=LSC stands for: Loss of,the consequences on the installation.#
I have open circuit measurements of 348,349,345,342 volts
And currents are 6 amps each under load at 230 volts
What I cannot easily get is the individual panel stats
It's just strange that all 4 strings are acting the same in this way under power scenario.

ISC

Short circuit current.

Similar to the VOC you measured, just a little more difficult to measure.

It’s easy to hit VOC, but a bad connector or panel will show piss poor ISC.

 

[seneysolar]

13 year old (polycrystaline?) panels probably wont make STC rating anymore. They degrade.

Have they been cleaned? Shoot, dust can kill 10%

Adjustable angle? You wont make STC rating with fixed ground mount but only a couple times a year in optimal conditions.

 

[keepsake]

Can you measure the Isc of the individual strings?

Just hook up one at a time into the inverter and see what you get for Vmp and Imp?

Give us more details on your panels, arrays, wiring, orientation, etc and we might be able to see a problem. Pictures are particularly useful.

Got more data ...

10 panels per string

Switched them in one at a time. Results are from inverter.
String 1 300w
String 2 900w
String 3 900w
String 4 900w

The open circuit voltages are: 345v,346v,342v,344v

So I went on the steep roof, to measure short circuit current as you suggested
panel 7 was 7.0 amps
panel 6 was 7.3 amps
panel 5 was 3.9 amps
So I took panel 5 out, panel 4 plus goes to panel 6 minus
Panel 5 has visible cracks that appeared to be below the surface.
Measured the inverter out again
String 1 is now 210 watts, down from 300w

Go figure. Later today I will tackle roof again. Clouds came in so readings will be useless.

You thoughts ?

 

[Quattrohead]

What we are not clear about yet is are two sets of strings paralleled together and if so where. It would be right before they get paralleled you would want to measure each string to narrow down your search field.
And yes, one knackered panel could very well show up as lots of voltage but bugger all current in that string.

 

[keepsake]

4 independent strings.
10 panels each string in series.
40 panels total.
No ties anywhere except at the negative and positive 350v ish
When new in 2011 this was close to 10 kw. Now down to 3 kw.
I added content to the post above from 1:27 pm today.

 

[ksmithaz1]

4 independent strings.
10 panels each string in series.
40 panels total.
No ties anywhere except at the negative and positive 350v ish
When new in 2011 this was close to 10 kw. Now down to 3 kw.
I added content to the post above from 1:27 pm today.

I'd put my money on those amazing mc4's. I fought a string of cs250's. Ended up replacing about 5 on a string of 8. Was making the output erratic.

 

[keepsake]

So it wasn't enough to exercise the connection(s) ? Pluggy in and out a few times ?
Did you replace with non-MC4 ?
For me at age 70 I might find it easier to replace panels at 40% with new ones.
Where do you/we have to trash these underproducing trash ?

 

[keepsake]

Do I buy new panels if they come with MC4's ?

 

[740GLE]

Do I buy new panels if they come with MC4's ?

Can you buy panels without MC4?

They can easily be snipped off and replaced with a connector of your choice.