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Solar panels are producing high voltage at night

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pproducts

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Hi

I am having problems with one of my arrays, 10 295w Canadian Solar panels in series. During the day it is producing about 340 volts and 8.5 amps and at night is is producing about 180 volts and .3 amps. I looked at my logs on solar assistance and it has been doing it every night for the last few months. It is generating power normally. I have an eg4 6000xp that it is hooked up to and I switched the array to mppt2 and the problem moved to mppt2 so that ruled out any problem with the inverter. I am thinking something is wrong with one of the solar panels but I really don't understand how they could be putting out 180 volt at night. It seems like the power would have to be coming from the inverter. This is 1 of 11 arrays and all other arrays are working correctly. Does anyone have any suggestions as what to look for?

Greg
 
Lt.Dan said:
Totally normal to have voltage at night, especially during full moons. You will not get any current from them though. At most 1 or 2w, nothing tangible.
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Hi

This is high voltage not the normal voltage you may see. Solar Assistant is reporting about 180volts and about 30-60watts. I have 10 other arrays that are currently reporting 0 volts and 0 watts.
 
How high up in the mountains do you live? It must be your elevation. The closer to the moon you are, the more moon power you get at night.

Maybe the angle on your other 10 arrays isn't lined up quite right to capture moonlight.

What you should be doing, is adjusting the other 10 arrays so you get moonlight power. 30-60 watts from moonlight on a 2950watt array is pretty darn good. I wish I got that.
 
cs1234 said:
How high up in the mountains do you live? It must be your elevation. The closer to the moon you are, the more moon power you get at night.

Maybe the angle on your other 10 arrays isn't lined up quite right to capture moonlight.

What you should be doing, is adjusting the other 10 arrays so you get moonlight power. 30-60 watts from moonlight on a 2950watt array is pretty darn good. I wish I got that.
Click to expand...
That sure would be nice but no moon out it is pitch black outside.
 
I did see a tiny amount of wattage from a Sunny Boy SWR2500U at night.
Calculation of yard lamp said that wasn't it.
I think something coupled over from grid AC and was rectified. The other several Sunny Boy didn't show same behavior, and this one didn't in the beginning.

AIO like you've got have a reputation for driving AC common-mode onto PV terminals.
You say you swapped around and the problem followed the PV string?

1) Check AC and DC voltage, common and differential mode. Day and night. Compare funny string with normal one.

2) Isolate PV string entirely from inverter. Repeat above tests on PV strings (normal and funny) and on inverter. For string, day and night. PV+ to ground and PV- to ground.

I'm guessing there is some path to ground, and the common-mode AC is getting rectified.
 
You could try covering the offending panels with a tarp or some cardboard or something at night.. just to make sure it's not any type of light.
 
Any overhead high voltage power transmission lines? I believe those can effect pv modules?
 
Disconnect that feed at the PV panels and see if it is coming from the panels or the wire back to the inverter.
 
pproducts said:
Solar Assistant is reporting about 180volts and about 30-60watts.
Click to expand...
Measure the voltage at the PV input to the inverter - sounds more likely a measurement / reporting error within the inverter, rather than actual power being generated.

cs1234 said:
Maybe the angle on your other 10 arrays isn't lined up quite right to capture moonlight.
Click to expand...
Sounds like a dual-axis moon tracking system is required here ;)
 
Hedges said:
I'm guessing there is some path to ground, and the common-mode AC is getting rectified.
Click to expand...
This is my bet. It happened to me. I was getting 50-70 watt hours overnight because I had a loose, empty wire to my combiner box laying next to the grounding rod. It took a bit of rain but it happened.
 
Thanks for all of the suggestions. I examined and tested every panel and found 3 bad mc4 connectors and also the mc4 connector on the main positive wire was needing to be replaced. The voltage returned to zero after dark tonight and everything is normal again.

Thanks for all the help.
Greg
 
pproducts said:
Thanks for all of the suggestions. I examined and tested every panel and found 3 bad mc4 connectors and also the mc4 connector on the main positive wire was needing to be replaced. The voltage returned to zero after dark tonight and everything is normal again.

Thanks for all the help.
Greg
Click to expand...
Bad connectors alone wouldn't do that. Perhaps you simply moved the wire out of the area where it was picking up voltage.
 
PotusGobbleBottom said:
Bad connectors alone wouldn't do that. Perhaps you simply moved the wire out of the area where it was picking up voltage.
Click to expand...
These were a temporary set I had laying on the ground. It looked like the mc4 connectors on one panel was in the middle of an ant hill and it was wet. It was very muddy and it was buried in the middle of it. The connectors were burned and loose. I think it may have been a grounding issue of some sort.
 
pproducts said:
These were a temporary set I had laying on the ground. It looked like the mc4 connectors on one panel was in the middle of an ant hill and it was wet. It was very muddy and it was buried in the middle of it. The connectors were burned and loose. I think it may have been a grounding issue of some sort.
Click to expand...
Fire ants? If so, I hope you got them good.
 
Hedges said:
I'm guessing there is some path to ground, and the common-mode AC is getting rectified.
Click to expand...
PotusGobbleBottom said:
This is my bet. It happened to me. I was getting 50-70 watt hours overnight because I had a loose, empty wire to my combiner box laying next to the grounding rod. It took a bit of rain but it happened.
Click to expand...
pproducts said:
These were a temporary set I had laying on the ground. It looked like the mc4 connectors on one panel was in the middle of an ant hill and it was wet. It was very muddy and it was buried in the middle of it. The connectors were burned and loose. I think it may have been a grounding issue of some sort.
Click to expand...

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PotusGobbleBottom said:
Bad connectors alone wouldn't do that. Perhaps you simply moved the wire out of the area where it was picking up voltage.
pproducts said:
These were a temporary set I had laying on the ground. It looked like the mc4 connectors on one panel was in the middle of an ant hill and it was wet. It was very muddy and it was buried in the middle of it. The connectors were burned and loose. I think it may have been a grounding issue of some sort.
Click to expand...
Click to expand...

So, in effect, you've just replicated the experiments that Luigi Galvani did with regard to animal electricity in 1771 🤣

 
Don't be surprised when you see it comes back. It's actually just that Solar Assistant is reporting the last value it received before your charge controller shut down for the day. When the sun goes down the controller shuts down, stops sending data and Solar Assistant continues to report the last value it saw from the controller as if you're generating power at night.
 
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