diy solar

diy solar

5.6kw solar array producing only 2kw during peak sun.

Fahmula

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Oct 7, 2020
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Here's the specs for the panels i'm using. I have a total of 20x400w panels with 6 in series facing east and a 7s2p facing south.
As i'm typing the east is producing 2.1k which is almost at peak but the south is also only doing 2.1k.

I'm using the DEYE hybrid 8k inverter which can handle up to 11kw of PV so i'm well below the limit.
It's weird that last Tuesday at this same time the total PV was 6.6kw with the south array doing 4.6kw. I'm actively turn on loads to try and push the panels just to make sure they get close to the rated power.

I'm using these branch connectors to parallel the south array strings which then feeds the two strings (east and south) to this DC disconnect before going into the MPPT of the inverter.

Is there anything wrong with this setup?
 
I think MC4 connectors are rated at 10A. You might try to break your 7s2p into just 7s and test each 7s string.....looking for any major difference.

Andy on the "Off Grid Garage" has been going nuts with a similar "low output" problem with some used panels that he has. You should watch some of his videos, posted the past 10 days or so. He still has not figured out the root problem.
 
If I understand you correctly, having 6S on one string and 7S on the other with the two strings in parallel is Egon bad. Your Voc and Vmp need to match, i.e., you need the same series voltage on your strings.

7S Voc: 375.5V
7S Vmp: 310.1V
6S Voc: 321.9V
6S Vmp: 265.8V

If the 7S is operating at it's Vmp, the 6S @ 310V is going to put out way less current than Imp. If the 6S is running at 265.8V, the power of the 7S will be substantially reduced by working at the lower voltage.

IMHO, rewire as 5S and 5S3P
 
If I understand you correctly, having 6S on one string and 7S on the other with the two strings in parallel is Egon bad. Your Voc and Vmp need to match, i.e., you need the same series voltage on your strings.

7S Voc: 375.5V
7S Vmp: 310.1V
6S Voc: 321.9V
6S Vmp: 265.8V

If the 7S is operating at it's Vmp, the 6S @ 310V is going to put out way less current than Imp. If the 6S is running at 265.8V, the power of the 7S will be substantially reduced by working at the lower voltage.

IMHO, rewire as 5S and 5S3P
The 6s string is not parallel at all. It goes straight to the MPPT. The other 14 panels are in two sets of 7 in series then parallel together.
 
I think MC4 connectors are rated at 10A. You might try to break your 7s2p into just 7s and test each 7s string.....looking for any major difference.

Andy on the "Off Grid Garage" has been going nuts with a similar "low output" problem with some used panels that he has. You should watch some of his videos, posted the past 10 days or so. He still has not figured out the root problem.
This test is a good idea. I'll give it a shot. I've been watching his videos lately.
 
I think MC4 connectors are rated at 10A. You might try to break your 7s2p into just 7s and test each 7s string.....looking for any major difference.

Andy on the "Off Grid Garage" has been going nuts with a similar "low output" problem with some used panels that he has. You should watch some of his videos, posted the past 10 days or so. He still has not figured out the root problem.

Most MC4 are rated for 30A.

The 6s string is not parallel at all. It goes straight to the MPPT. The other 14 panels are in two sets of 7 in series then parallel together.

So each array goes to its own MPPT?

What is the current limit on the MPPT? I don't know if it's the right unit, but https://www.deyeinverter.com/deyeinverter/2021/04/12/【b】hybridinvertersun-8-10-12k-sg04lp3.pdf indicates 13A max, and you're inputting 18A meaning that array is never going to produce more than 13/18 = 72% of rated.

Given that, @DThames suggestion should yield the sum of the strings is not 2X the power of the strings.
 
So each array goes to its own MPPT?

What is the current limit on the MPPT? I don't know if it's the right unit, but https://www.deyeinverter.com/deyeinverter/2021/04/12/【b】hybridinvertersun-8-10-12k-sg04lp3.pdf indicates 13A max, and you're inputting 18A meaning that array is never going to produce more than 13/18 = 72% of rated.

Given that, @DThames suggestion should yield the sum of the strings is not 2X the power of the strings.
This is the manual that came with my inverter https://drive.google.com/file/d/1wJlV_Gwgnf8nUgMVAtgJer2885rQYwFf/view?usp=sharing
It is similar to the one you shared but mine has 18A for each of the MPPT. You can see examples of PV strings in the manual I shared too. Remember that I also stated that the panels was producing more last week in the same weather conditions.
 
Screen Shot 2021-04-29 at 1.01.05 PM.png

This data was on 4/21 just over a week ago. PV1 is the 6S strings facing east and PV2 is the 7S2P facing south. That's the highest I ever saw my system did. the reason why I had to go this far back is because from the day forward I stop trying to push the panels as much as I can and just used electricity normally. This PV system is located in Jamaica for my vacation house.
 
Grab a clamp DC ammeter and check current flowing through each string.

Confirm there is 0 shade anywhere on any panel.

Confirm you're not in absorption and current limited on the battery. I know you've said you're trying to increase loads, but I'm just trying to cover the basics. To be sure, you likely need at least 4kW of loads.
 
Grab a clamp DC ammeter and check current flowing through each string.

Confirm there is 0 shade anywhere on any panel.

Confirm you're not in absorption and current limited on the battery. I know you've said you're trying to increase loads, but I'm just trying to cover the basics. To be sure, you likely need at least 4kW of loads.
No shade, clear blue sky and 80F outside. Gonna go check each string now.
 
Grab a clamp DC ammeter and check current flowing through each string.

Confirm there is 0 shade anywhere on any panel.

Confirm you're not in absorption and current limited on the battery. I know you've said you're trying to increase loads, but I'm just trying to cover the basics. To be sure, you likely need at least 4kW of loads.
So I just got off the roof. With either strings connected by itself i'm getting 9A but as soon as I parallel them, one string shows 0A and the other 8.6A. What could cause this to happen?
 
So I just got off the roof. With either strings connected by itself i'm getting 9A but as soon as I parallel them, one string shows 0A and the other 8.6A. What could cause this to happen?
I had kinda similar issue, my inverter only allows 10A per string/input, I had to separate them and never had this problem again.
 
I had kinda similar issue, my inverter only allows 10A per string/input, I had to separate them and never had this problem again.
It's very weird because the spec sheet states 18A per MPPT and it was working last week. It stoped working after my installer had messed up the pins in one of the MC4 connectors. He used 2 male instead of a female and male pin. I realized this on the 26th when the 14 panel array was showing zero volts and when he checked the connector it was literally burning.
I'm wondering if that damaged the Y connector somehow, tho I test both array at either port on the Y connector and they both work independently but not together.
 
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Sounds frustrating!

I'm uncertain what is causing your problem in specific on this occasion given the info available.
edit: ack! hot connector! hope you can get things low ohm town soon!

Maybe a bad connection? Sometimes I use a seek thermal camera (kinda pricey, ~250usd) to diagnose electrical issues, or just do verification. A hot connector could give away the mystery potentially.

Anyways, without assuming what the problem is, I wanted to share this anecdote shortly.
I ran a single underground feeder cable in yard for a small DIY solar thing (0.6kWp), and in my paranoia, I soldered all four MC4 connectors to the solid copper. A tug test even with the nice 10AWG stranded copper PV wire made me feel inclined to just solder every single MC4 connector I ever make. An extra 5 minutes per connector on my part to feel very certain about the entire circuit. /anecdote

hope you can get to the bottom of this soon?
 
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Sounds frustrating!

I'm uncertain what is causing your problem in specific on this occasion given the info available.

Maybe a bad connection? Sometimes I use a seek thermal camera (kinda pricey, ~250usd) to diagnose electrical issues, or just do verification. A hot connector could give away the mystery potentially.

Anyways, without assuming what the problem is, I wanted to share this anecdote shortly.
I ran a single underground feeder cable in yard for a small DIY solar thing (0.6kWp), and in my paranoia, I soldered all four MC4 connectors to the solid copper. A tug test even with the nice 10AWG stranded copper PV wire made me feel inclined to just solder every single MC4 connector I ever make. An extra 5 minutes per connector on my part to feel very certain about the entire circuit. /anecdote

hope you can get to the bottom of this soon?
Since I know both of the series panels are working, I think the issue lies with the Y connectors. I contacted my installer and since this could stem from the MC4 connector being wrong installed, he’ll add another string and provide the extra PV wire free of cost. Hopefully this should solve the issue and worst case I can narrow it down a lot.
 
Likely poor contact on one of the MC4. Had a similar situation where all components would measure fine, but as soon as they were strung together... 0V. Traced it to a single MC4 connector on a single patch cable. Cut and replaced and fixed.

I'd have him swap out anything he messed up.
 
It's very weird because the spec sheet states 18A per MPPT and it was working last week. It stoped working after my installer had messed up the pins in one of the MC4 connectors. He used 2 male instead of a female and male pin. I realized this on the 26th when the 14 panel array was showing zero volts and when he checked the connector it was literally burning.
I'm wondering if that damaged the Y connector somehow, tho i test both array at either port on the Y connector and they both work independently but not together.
To be honest with you, I don't trust the Y connectors at all, had the same problem, my inverter was shutting down, error message: ARC fault, I had to re-crimp the MC4 connectors
 
Likely poor contact on one of the MC4. Had a similar situation where all components would measure fine, but as soon as they were strung together... 0V. Traced it to a single MC4 connector on a single patch cable. Cut and replaced and fixed.

I'd have him swap out anything he messed up.
I'll definitely have him double check all the connectors with me.
 
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