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Are my panels underperforming?


Chris_S

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I installed a 8S string of JA 550W panels. On a single sunsynk mppt. I've been watching the panels the last two days as we've had clear skies and cool weather. Max PV I've got at around 12pm each day is 3.7kw. The 8 panels should provide 4.4kw. Facing north at 20 degrees inclination. 

I checked the OCV and it was 377V in full sun. According to the panels it should be 399V. Panels look clean. Cable length is about 30m and I've used 4mm2 solar cable. 

Any suggestions? 

IMG_20230130_174628_resized_20230326_024602504.thumb.jpg.330dc2ce8db39187a3311630acfa93f7.jpg

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1 minute ago, zsde said:

Production will be determined by the load at the time. Check your load at the same time that you observed the 3,7kW.
 

Best way to check is to switch on tons of stuff on a nice clear,cool if possible day around midday and then your mppts in the inverter will give you the best they can and then you have your answer.I have 6kw of panels and the best I got was 5.6 kw

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1 minute ago, Nicholas Strachan said:

Best way to check is to switch on tons of stuff on a nice clear,cool if possible day around midday and then your mppts in the inverter will give you the best they can and then you have your answer.I have 6kw of panels and the best I got was 5.6 kw

We pushed them yesterday. Battery was low. We ran the tumble dryer, dishwasher and vacuum all at once. Load was 5kw. 3.6kw came from the panels the rest came out the battery. Sky was clear and a cool day. I notice that I got 12.5A from the panels which is close to max but the mppt dropped the voltage to 310V. When panels are covering lower loads the mppt voltage is around 360V

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14 minutes ago, Nicholas Strachan said:

If I understand correctly the amps will be clipped by the inverter if they are too high but the excess voltage will fry the inverter but yours are within limits.I assume no shading on the panels.The panels might look clean but still have ingrained dirt on them.Worth trying a clean and then see.

I think I'll give them a clean. Only been up a few weeks though but there was a big bird s#*t on them a week ago but looks like the rain did wash it off. Might need a better clean

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There were panels sold cheaper a while ago on an online store that were below manufacturer specs. Just can't remember which store that was. I just hope mine never came from that same wholesaler. I'm going to try get Canadian solar for my next string then I can really compare. 

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I have 8 x JA Solar 540W panels, live in East london which has a solar potential about as low as it gets in South Africa. The Victron Energy MPPT calculator does show a fairly significant drop in solar potential in March. Even so, today I achieved a peak of 4,7 kW and a 15 min average production of over 3,7 kW at 11:30. In Dec / Jan and Feb, my panels consistently delivered more than their rated capacity with peaks of over 5,3kW and 15 min averages of above 4,5 kW. Panels are mounted 16 deg E of N, 26 deg inclination.

My panels have been up for 13 months and yet to be cleaned. Yes I know it should be done regularily but I need to find someone a lot younger than I am to clamber around on my roof.

There are free tools on the internet to predict performance. Here is one of them - https://solcast.com/free-rooftop-solar-forecasting.

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14 minutes ago, Peter V said:

I have 8 x JA Solar 540W panels, live in East london which has a solar potential about as low as it gets in South Africa. The Victron Energy MPPT calculator does show a fairly significant drop in solar potential in March. Even so, today I achieved a peak of 4,7 kW and a 15 min average production of over 3,7 kW at 11:30. In Dec / Jan and Feb, my panels consistently delivered more than their rated capacity with peaks of over 5,3kW and 15 min averages of above 4,5 kW. Panels are mounted 16 deg E of N, 26 deg inclination.

My panels have been up for 13 months and yet to be cleaned. Yes I know it should be done regularily but I need to find someone a lot younger than I am to clamber around on my roof.

There are free tools on the internet to predict performance. Here is one of them - https://solcast.com/free-rooftop-solar-forecasting.

Well what do you know I'm also in East London. So we both had the same weather the last 2 days. You had a peak of 4.7kw and my highest peak was 3.7kw. My panels are also just E of N and at 20 degrees. 

So something is off. 

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8 minutes ago, Chris_S said:

Well what do you know I'm also in East London. So we both had the same weather the last 2 days. You had a peak of 4.7kw and my highest peak was 3.7kw. My panels are also just E of N and at 20 degrees. 

So something is off. 

Perhaps not. It depends on how your inverter is reporting. My peak is reported by the software controlling the MPPT, whilst the average by the inerter controller. Maybe our 3,7 kW are the same thing.

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9 minutes ago, Peter V said:

Perhaps not. It depends on how your inverter is reporting. My peak is reported by the software controlling the MPPT, whilst the average by the inerter controller. Maybe our 3,7 kW are the same thing.

Yeah that as well. So could be the same. What time does your production start dropping? 

I need to cut some trees. I'm dropping off at 2:30pm right now but that's when shadows start. 

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53 minutes ago, Chris_S said:

Yeah that as well. So could be the same. What time does your production start dropping? 

I need to cut some trees. I'm dropping off at 2:30pm right now but that's when shadows start. 

You have a good benchmark from Peter V. Just for starters the 4.4 kW as per the specs of the 8 panels in lab tests of 1000W/sq m you could adjust that down to about 75% in your area. Thus they are performing reasonably well. During cloud edge you could get quite a bit more but that only lasts a minute or 2.

Your Voc is also within specs. Your 12.5A and voltage under load is also good for your area with lower irradiation.

Your 30m run is not a problem as I don't loose much with a 40m run cable length from panels to inverter.

Edited by Scorp007
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My 2c, those numbers look normal for end of March, during Dec/Jan I was getting 5.4KW from my 6KW Array. Now I am getting 4.5KW. Granted my angles are not even close to optimal but the sun is a lot weaker compared to mid summer. After the weekend's rain the panels where nice and clean and I saw some 5KW peaks yesterday (cloud edge effect)

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The 20 degree tilt could account for a 3.5% loss, and then there's the tolerance in power, which is another 3.5%, but that's not explaining it by itself.

Testing some theories - what battery do you have connected, with what charging amps? Had a thread recently where the problem was resolved by increasing the battery's ability to take accept greater charge.

Other than that, would be curious to know if splitting the string across the two MPPTs would make a difference. Not making a statement, more like asking a question from anyone who knows better how much power can be connected to one MPPT even if the Voltage and current are in spec. Seen some threads on the topic, but don't know the answer.

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6 minutes ago, GreenFields said:

The 20 degree tilt could account for a 3.5% loss, and then there's the tolerance in power, which is another 3.5%, but that's not explaining it by itself.

Testing some theories - what battery do you have connected, with what charging amps? Had a thread recently where the problem was resolved by increasing the battery's ability to take accept greater charge.

Other than that, would be curious to know if splitting the string across the two MPPTs would make a difference. Not making a statement, more like asking a question from anyone who knows better how much power can be connected to one MPPT even if the Voltage and current are in spec. Seen some threads on the topic, but don't know the answer.

Hi. 

It's a DIY 230Ah battery with seplos BMS. Charging amps set to 115A so plenty to go to reach that rate. 

Will be interesting when I put another string on the other mppt. I'll let you know. 

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