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Please help interpret solar data


SiriS

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Hi there, some advice for a noob please.

I have 18x545W = 9.8kW panels. I don't recall how the 2 MPPTs are arranged, but for the last 2 months they have contributed roughly 50% each towards solar input every time I've checked (which is often :))

Today, for the first time, I noticed a big discrepancy with MPPT2 producing almost half of MPPT1. I've also attached the Sunsynk app input charts, but not really understanding it and whether it indicates an issue. It does look like there is a big discrepancy between the 2 MPPTs though.

IMG_4149.thumb.jpeg.f01c14fc6a2380d36059021d9031edfd.jpeg

 

IMG_4154.thumb.jpeg.c6bea2912e9bd8e96b3e4bc49c4f9598.jpeg

 

I just climbed up the roof, there are no shadows, the whole array faces slightly East of North. It is now 14:15 so sun is NW. 

With the solar panel layout I also wouldn't expect substantial production differences?

IMG_3193.jpeg.9bb42d0a77ad54a25d932b9e0b8bd50b.jpeg

 

Appreciate any advice and possible reasons for difference.

Thank you! 🙏

 

 

 

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Looks like your battery is fully charged which will result in the reducing of power being pulled from the panels. 

I assume that all your panels are facing the same direction and no shadding as you said. 

My guess is that you may have either a bad connection somewhere or a dodgy panel pulling down the amperage of the whole string. 

You could swop your strings around on your inverter to confirm it is a string issue and not the MPPT controller (not likely). 

If you have a Flir camera you can check the panels with it, a hot spot will show up pretty quickly, otherwise look carefully at the panels for small cracks. 

image.png.582d9e20409fc5babeb9edb8f07352ae.png

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Just some pure speculation, which you could check with your installer.

To the right of the image, seemingly on a lower level, it looks like you've got a further 6 panels, but I'm going on the understanding that those are for a different purpose, not involved with this issue.

On your main roof section you're showing what looks like 18 panels, laid out in 3 strings of 6 panels each, and this is what I assume are the panels in question.

I think it's likely that you've got 2 of those strings in parallel on MPPT1, and the third string by itself on MPPT2. I say this because the Voltage on each MPPT is the same, while the current on MPPT1 is roughly double that of MPPT2.

At this point it would be interesting to know the voltage and current specs of your 545W panels to verify if that suspected layout makes sense. It might also help if you can confirm what combiner boxes you have installed.

What I suspect is that the discrepancy in power generation is more pronounced at this time of the year because of the lower sunlight in late autumn as we're going into Winter.

MPPT2 is probably outputting near to the peak power that it can manage in the lower available light - it can probably push closer to 10A during summer, but MPPT1 can continue to produce higher current because of the two strings of panels connected to it.

But as I said, this is some kansvattery, just some thoughts to be checked out.

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3 hours ago, Sc00bs said:

My guess is that you may have either a bad connection somewhere or a dodgy panel pulling down the amperage of the whole string. 

You could swop your strings around on your inverter to confirm it is a string issue and not the MPPT controller (not likely). 

Thanks, going to monitor a bit and then have my installer check for me if I can't solve. 

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3 hours ago, GreenFields said:

Just some pure speculation, which you could check with your installer.

To the right of the image, seemingly on a lower level, it looks like you've got a further 6 panels, but I'm going on the understanding that those are for a different purpose, not involved with this issue.

On your main roof section you're showing what looks like 18 panels, laid out in 3 strings of 6 panels each, and this is what I assume are the panels in question.

I think it's likely that you've got 2 of those strings in parallel on MPPT1, and the third string by itself on MPPT2. I say this because the Voltage on each MPPT is the same, while the current on MPPT1 is roughly double that of MPPT2.

At this point it would be interesting to know the voltage and current specs of your 545W panels to verify if that suspected layout makes sense. It might also help if you can confirm what combiner boxes you have installed.

What I suspect is that the discrepancy in power generation is more pronounced at this time of the year because of the lower sunlight in late autumn as we're going into Winter.

MPPT2 is probably outputting near to the peak power that it can manage in the lower available light - it can probably push closer to 10A during summer, but MPPT1 can continue to produce higher current because of the two strings of panels connected to it.

But as I said, this is some kansvattery, just some thoughts to be checked out.

Thank you, I didn't consider that. I assumed 9 panels per MPPT, but I could be wrong maybe it is 12/6 like you suggest. That would certainly explain the often double output at higher watts and maybe more pronounced now in autumn as you say.

Food for thought, further investigations will need to be done, thank you for your kansvattery :)

PS the lower level panels are my neighbour's 

 

 

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5 hours ago, GreenFields said:

 

On your main roof section you're showing what looks like 18 panels, laid out in 3 strings of 6 panels each, and this is what I assume are the panels in question.

 

This would be unlikely, both MPPTs are at about 370V, if there is only 6 panels in serie on one of the MPPTs then it means each panel is producing 60 volts which is either very impressive or very unlikely.

It is more likely to be 9 in serie on each MPPT which equals to an operating voltage of 41V per panel which is right in the pallpark for 535w panels.

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7 hours ago, SiriS said:

Hi there, some advice for a noob please.

I have 18x545W = 9.8kW panels. I don't recall how the 2 MPPTs are arranged, but for the last 2 months they have contributed roughly 50% each towards solar input every time I've checked (which is often :))

Today, for the first time, I noticed a big discrepancy with MPPT2 producing almost half of MPPT1. I've also attached the Sunsynk app input charts, but not really understanding it and whether it indicates an issue. It does look like there is a big discrepancy between the 2 MPPTs though.

IMG_4149.thumb.jpeg.f01c14fc6a2380d36059021d9031edfd.jpeg

 

IMG_4154.thumb.jpeg.c6bea2912e9bd8e96b3e4bc49c4f9598.jpeg

 

I just climbed up the roof, there are no shadows, the whole array faces slightly East of North. It is now 14:15 so sun is NW. 

With the solar panel layout I also wouldn't expect substantial production differences?

IMG_3193.jpeg.9bb42d0a77ad54a25d932b9e0b8bd50b.jpeg

 

Appreciate any advice and possible reasons for difference.

Thank you! 🙏

 

 

 

I know you said there is no shade, but this just looks very much like shade. Did you check all the cells on all the panels, all you need is one cell on one panel to be shaded and you will get this effect. With the seasons changing the sun is moving lower in the horizon and also moving more northerly. Often shade issues only make themselves known as the seasons change.

It might also be a loose MC4 connector (or poorly crimped wire) or a diode failure in one of the panels.

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17 hours ago, SiriS said:

Hi there, some advice for a noob please.

I have 18x545W = 9.8kW panels. I don't recall how the 2 MPPTs are arranged, but for the last 2 months they have contributed roughly 50% each towards solar input every time I've checked (which is often :))

Today, for the first time, I noticed a big discrepancy with MPPT2 producing almost half of MPPT1. I've also attached the Sunsynk app input charts, but not really understanding it and whether it indicates an issue. It does look like there is a big discrepancy between the 2 MPPTs though.

IMG_4149.thumb.jpeg.f01c14fc6a2380d36059021d9031edfd.jpeg

 

IMG_4154.thumb.jpeg.c6bea2912e9bd8e96b3e4bc49c4f9598.jpeg

 

I just climbed up the roof, there are no shadows, the whole array faces slightly East of North. It is now 14:15 so sun is NW. 

With the solar panel layout I also wouldn't expect substantial production differences?

IMG_3193.jpeg.9bb42d0a77ad54a25d932b9e0b8bd50b.jpeg

 

Appreciate any advice and possible reasons for difference.

Thank you! 🙏

 

 

 

Are those 6 bottom panels behind that little wall? Even a small shadow across all 6 panels can halve the amperage

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Thanks everyone for all the very instructive replies. It seems like shading might be the culprit after all - the parapet is slightly higher than the bottom of the solar panels, so it is a creating a small shadow area.

Very small, but substantial impact!

IMG_4152.thumb.jpeg.9ca48d1af05b64d7c46c6f84a25e3d9c.jpeg

Back to the drawing board to try to solve. 

Thank you 🙏

 

 

 

 

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49 minutes ago, SiriS said:

Thanks everyone for all the very instructive replies. It seems like shading might be the culprit after all - the parapet is slightly higher than the bottom of the solar panels, so it is a creating a small shadow area.

Very small, but substantial impact!

IMG_4152.thumb.jpeg.9ca48d1af05b64d7c46c6f84a25e3d9c.jpeg

Back to the drawing board to try to solve. 

Thank you 🙏

 

 

 

 

And with half cut panels it will basically turn off all bottom halves of that row and as such half the amperage. Low winter sun sucks. 

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You could add panel optimisers onto the bottom row of panels, not sure of it would be worth the effort though. May be better to just remove the row of bricks dropping the shade on the panels .

Optimisers won't change the power the shaded panels are producing but stops them from pulling the whole strings amperage down by converting volts to amps. 

Power = Volts x Amps

So, the panels in the shade are producing 4.9A @ 40V ea = 196W each

The ones in the full sun are producing 9.2A @ 40V = 368w 

Fitting optimisers to the bottom row will drop the voltage and increase the amperage of each panel so as not to pull the whole string down.  

  4.9a @ 40v - 9.2a @ 21V so your string voltage will be 246V @ 9.2A = 2263W vs 1813W without optimisers

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Do you feed in to the grid?

Is it not possible that due to your batteries being full, the PV is being limited to your load?

Maybe check if the same thing happened the previous few days? Or even next few days as I see this post is a couple of days old. 

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