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Solar production get worse after replacing brand new panels

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flashmark

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Nov 4, 2022
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On my house's roof, I had 375 W (JA) 6 panels (used). In the peak hours, the production was 2.2 KW. (375x6 = 2250. Recived 2.2 KW which is amazing)
But that wasn't enough to charge my battery fully.
So I have installed five 545W (JA) panels (brand new). But now the production is reduced to 2000 in peak hours.

When there was a 2250W panel (since panels connected in parallel behave as one single panel), output was 2200 W. But with a 2725 W panel, peak output is 2 KW.
I can not believe why it is drastically reduced with brand new panels. I was expecting at least 2.5KW KW during peak hours.

My lifePo4 battery pack is 9.6Kv. It was discharged at that time. Charging t set to 80A in mppt (I didn't change any setting during the transition)

Can someone explain this behaviour.
 
Last edited:
timselectric said:
Panels only provide what is required.
Were your loads satisfied?
Click to expand...
The peak charging rate is set at 80 A. I didn't change when replacing the panels. My lifePO4 battery pack is 9.6 kV. It was discharged fully at the time I measured the peak W.
 
What are the specs for your charger and what are the specs of the panels? I believe your answer is there.
 
flashmark said:
The peak charging rate is set at 80 A. I didn't change when replacing the panels. My lifePO4 battery pack is 9.6 kV. It was discharged fully at the time I measured the peak W.
Click to expand...
I would check all connections.
With the panels in parallel. A bad connection wouldn't be noticeable. Other than low overall production.
 
flashmark said:
On my house's roof, I had 375 W (JA) 6 panels (used). In the peak hours, the production was 2.2 KW. (375x6 = 2250. Recived 2.2 KW which is amazing)
But that wasn't enough to charge my battery fully.
So I have installed five 545W (JA) panels (brand new). But now the production is reduced to 2000 in peak hours.

When there was a 2250W panel (since panels connected in parallel behave as one single panel), output was 2200 W. But with a 2725 W panel, peak output is 2 KW.
I can not believe why it is drastically reduced with brand new panels. I was expecting at least 2.5KW KW during peak hours.

My lifePo4 battery pack is 9.6Kv. It was discharged at that time. Charging t set to 80A in mppt (I didn't change any setting during the transition)

Can someone explain this behaviour.
Click to expand...
Since you replaced panels with physically larger ones I wonder if the new arrangement is getting full sun light? Is the mount angles the same? Is it possible that you have a bad connection somewhere? BTW whether in parallel or series the wattage adds up. It is just your voltage and amperage that changes on how it equals the wattage. If panels are not equal in rated voltage and amperage but connected (P or S) it will effect total wattage.
 
timselectric said:
I would check all connections.
With the panels in parallel. A bad connection wouldn't be noticeable. Other than low overall production.
Click to expand...
We didn't change any connectors. used existing connections used for 375W panels. Do I need to check the MC4 connectors? If it is the case will the array work but produce a lower W?
 
We need to know how they are connected series and parallel, we need to know the voltage and current rating of the panels and the voltage and current capacity of your mppt charger. Then you might get some actual answers. And readings from your system.
 
Your “problem” has to do with the higher current of the newer big panels.
The 375 Wp has 9.4 A at max mppt
The 545 Wp has 13 A at max mppt

Your inverter/mppt is most likely maxed for 10 A current input for the “old style” (read smaller) solar panels.. And because you went down from 6 to 5 panels the maximum power that your inverter can produce is now limited.
6 (375 Wp) panels x 9.4 A x 40 V = 2256 W
5 (545 Wp) panels x 10 A x 40 V = 2000 W

I know of more people that forget to check the max current specs off their inverter, specially with these new big panels.

The solution for you is a new inverter that can handle 13 A input current.
With that you’ll have 5 x 13 A x 40 V = 2600 W.
 
Last edited:
flashmark said:
My lifePo4 battery pack is 9.6Kv.
Click to expand...
EDIT: BAD MATH, disregard (Thanks TomC4306)

I don't understand what this means. 9.6 kV would be 9600 Volts. I'm pretty sure that's not right! If you mean 9.6 kWh, e.g. a 48V / 200 Ah system, then your 80A MPPT controller will limit charging to roughly 50V * 80 A = 2000 W. It doesn't matter if you have a 5000 W array, you'll still get roughly 2000 W.

Charging voltage is lowest at 0% SOC then gradually rises as the battery charges. So you may start out charging at 45V * 80A = 1800W and peak at 52V * 80A = 2160W or whatever. The MPPT will adjust panel output accordingly (and panel output will be 5-10% greater than charging power due to losses in the MPPT itself).
 
Last edited:
Is the amount of sunlight same or different? If you don't measure it, you will never know.
In the absence of a light meter, one PV panel fed through an ammeter and oriented same as array should be perfect.

Could be voltage/current limit of inverter vs. panels, as Pim57 said. But only if conditions are such that you run into one of the limits.
Cool, clear day is a good time to get max current.

To some extent, MPPT can find a higher voltage, lower current fairly close to maximum power. Examine I/V and power/V curves of panels if you have suitable graphs and/or are mathematically inclined.
 
flashmark said:
We didn't change any connectors. used existing connections used for 375W panels. Do I need to check the MC4 connectors? If it is the case will the array work but produce a lower W?
Click to expand...

There have been threads here on the forum where MC4 connectors were the culprit in poor, or zero, PV performance. Take the MC4 connectors apart and carefully inspect the crimps and contact surfaces. Note that I'm not denigrating all MC4 connectors. It's usually a cheap MC4 connector, incorrect crimping or even mismatched MC4 connectors.
 
Pim57 said:
Your “problem” has to do with the higher current of the newer big panels.
The 375 Wp has 9.4 A at max mppt
The 545 Wp has 13 A at max mppt

Your inverter is most likely maxed for 10 A current input for the “old style” (read smaller) solar panels.. And because you went down from 6 to 5 panels the maximum power that your inverter can produce is now limited.
6 (375 Wp) panels x 9.4 A x 40 V = 2256 W
5 (545 Wp) panels x 10 A x 40 V = 2000 W

I know of more people that forget to check the max current specs off their inverter, specially with these new big panels.

The solution for you is a new inverter that can handle 13 A input current.
With that you’ll have 5 x 13 A x 40 V = 2600 W.
Click to expand...
This is not a old inverter. As I mentioned in my question I set it to 80A (though my inverter can handle 100A)
 
Hedges said:
Is the amount of sunlight same or different? If you don't measure it, you will never know.
In the absence of a light meter, one PV panel fed through an ammeter and oriented same as array should be perfect.

Could be voltage/current limit of inverter vs. panels, as Pim57 said. But only if conditions are such that you run into one of the limits.
Cool, clear day is a good time to get max current.

To some extent, MPPT can find a higher voltage, lower current fairly close to maximum power. Examine I/V and power/V curves of panels if you have suitable graphs and/or are mathematically inclined.
Click to expand...
There was no difference in the amount of sunlight. Even though it is difficult to say with certainty without a light meter, there is a lesser possibility of losing 700 watts during peak hours.
The MPPT controller can handle upto 100A but I set it to 80 A. So that can not be the case.
 
I read some articles, and according to those, in the first few days or weeks there will be less production from panels due to the protective coating on the panels.
If it is not, there can be an issue with MC4 connectors.
A third option would be to check panel by panel and measure the production of each panel. This will be a difficult task because to turn on my inverter requires at least four panels. There is no meter to check them one by one.

Thanks for your input.
 
HRTKD said:
Link to the data sheet for the inverter/mppt?
Click to expand...
400bird said:
How about the inverter/charge controller?
Click to expand...
makeskyblue.com

6.6KW Pure Sine Wave MPPT Solar Inverter, 48V DC to 220V AC, Off&On Grid Tie Inverter, No battery inverter, High PV inverter

6KW Pure Sine Wave MPPT Solar Inverter, 48V DC to 220V AC This is a multi-function inverter/charger, combining functions of inverter, MPPT solar charger, and battery charger to offer uninterruptible power support with portable size. Its comprehensive LCD offers user-configurable and...
makeskyblue.com makeskyblue.com
 
flashmark said:
makeskyblue.com

6.6KW Pure Sine Wave MPPT Solar Inverter, 48V DC to 220V AC, Off&On Grid Tie Inverter, No battery inverter, High PV inverter

6KW Pure Sine Wave MPPT Solar Inverter, 48V DC to 220V AC This is a multi-function inverter/charger, combining functions of inverter, MPPT solar charger, and battery charger to offer uninterruptible power support with portable size. Its comprehensive LCD offers user-configurable and...
makeskyblue.com makeskyblue.com
Click to expand...

"Please download the PDF manual from here."

But no link to download.

We're looking for the number of MPPT inputs, and max input current per MPPT. That's missing from the web page.
 
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