Solarpanels poor performans

[Chris Louw]

2 Strings Jinko panels 3 x 750 watt produce only 860 watt .Panels are 3 years old .

Checked  both strings . Results  1) 99 Voc   7.7 Amp.    2) 89.9Voc.  7.66 amp . Panels dit perform better when installed .Please any info would help

 

[Chris Louw]

Sorry should be 3 x 250 watt panels

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4 hours ago, Chris Louw said:

750 watt produce only 860 watt

That sounds like they are producing above their STC rating. What's the problem?

[Chris Louw]

It is 2 strings of 3 panels 750 watt should be about 1400 watt . Thanks .

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29 minutes ago, Chris Louw said:

It is 2 strings of 3 panels 750 watt

Aaah! Fair enough, that's a problem :-)

So those are 60-cell modules? I'd expect them to be around 90V when at their maximum power point... which they are. Are they dirty perhaps?

Are they on seperate MPPTs? You list two voltages, so  I assume yes. One makes 100V at  amps, the other about 90V at the same current, so both make in excess of 600W. How come the total only amounts to 860W?

Something doesn't add up.

[Chris Louw]

The strings was disconnected .Sorry the one string was 99 volt and the other 98.9 the current was 7.7 and 7.66 The spec is OCV 37.7 V and 8.2 amp . I not sure about the amount of cells , will have to check tomorow . 30.6 volt and  max 8.61Amp is also on the speck sheet . We had lots of rain ,the panels is nice and clean . When connected to mppt only 860 is available . Check mppt with other panels and is fine (85% efficient ) My electric knowledge is basic . Is it bad panels or can i check something.

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Well, some things to try would be to connect just the one string and see how much that makes, then connect just the other one and check how much that makes, then connect both and see how much that makes, etc etc. What you expect to see is 700W (ish) with either string and 1400W when combined. Maybe you see something obvious like one string making less than expected, or maybe they work well individually but not when combined. If both are low individually (eg only make 300W-400W in full sunshine), then you start looking at connections, dirty panels, etc. As I sometimes say, don't guess, turn on Dummy Mode and just try obvious things that should work... and when they don't, that's the smoking gun.

Going on what you posted already, it seems they work well individually, but when combined doesn't go over 900W or so.

Seasonal change perhaps? Tree grew up? One array is shadowed?

[Chris Louw]

That was what i tried . Connect string no 1 produce +-330 watt . Connect string no 2 produce +-340 watt . Connect no 1 and 2 produce +-680 watt . Then i connect 2 other strings alone produce +- 1400 watt . Then connected all 4 strings produce 2070 watt .Praying all the time that the sun stays the same . So  I presume the readings is right . Same wire size on all panels , only difference the wires on low reading 2.5 meters shorter . Checked all connections and replaced 1 combiner which was laying in the cannel full of water . No inprovement . Is there anything else i can check . These 2 panels (poor power ) was installed 3 years ago and was producing +- 1250 then .What a day .  Have a good evening .

[pilotfish]

2 hours ago, Chris Louw said:

one string was 99 volt and the other 98.9 the current was 7.7 and 7.66

1. String test #1 = 99 X 7.7 = 762 >> no problem,
2. String test #2 = 98.9 x 7.66 = 757 >> no problem.

From the above I don't think your panels are a problem. Maybe the MPPT is adjusting to draw only what it required (unless I misunderstood your test data).

 

[pilotfish]

@Chris Louw In a previous thread you mentioned running 15x 250w panels on a single Axpert, but having another 3 panels and another Axpert available. Have you made any changes to the system and if so what is the current description.

[Chris Louw]

No changes was made . I was getting ready to install a 2nd inverter . These 2 strings would be connected to The 2 nd inverter . As Chris Hobson advice I would have 4 strings on the old inverter and 2 on the new inverter . It would also be best for my layout . Less wires .That is when I found out that someting was wrong with these 2 strings . I did the test on both inverters , same results .If i have some time I will try and get volt and current readings with these 2 strings when connected  and working . 12 Months ago I addid the last 3 panels to make it 5 strings . The inverter produced +- 3000 watts . We rarely go over 2500 watts to keep the system happy with a big safety margin . The string we add  now is for cloudy days and to exstend the systems supply for future years at a good  2500 watts . Hope I expressed myself clear . Thanks for your interest .

[Chris Louw]

Some more info on test . All test were done with a load bigger than the connected strings capacity to get a total reading avialable . Have a good evening .

[pilotfish]

I suggest making the full change and installing the 2 strings on the second inverter as planned - a lot of factors can effect the output from an MPPT and the data that you provided earlier does not indicate any problems with the panels.

Don't forget to download and implement the Axpert Parallel Manual from the download section.

 

[Chris Louw]

Thanks i have the manual

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13 hours ago, Chris Louw said:

Connect string no 1 produce +-330 watt . Connect string no 2 produce +-340 watt

But that does not match the first test where you said +-90V at 7 amps for both, which should have made > 600W on those strings.

Well, you swapped over the inverters and the panels, so it sounds like the MPPT is good. Then it must be the wiring or the panels themselves.

[Chris Louw]

Thanks will check everything again

[Chris Louw]

Thank you for your advice Chris , Plonkster , Pilotfish . The 2 x Axpert in parallel with 6 x 3 strings 250 watt is running . Had only one problem . System was performing bad until I picked up in one of the manuals that a parallel system can only run SBU or Utility ( Program 1 ) We have a lot of cloudy days lately but this morning was bright sunshine . I am happy with the system . Is it really worthwhile to upgrade the firmware . Currently running 52 - 30