Hmm yea something not right

[Prettyaimless]

Ok for background i have a small off grid system where i spend my summers. Its a 300 amh lifepo4 battery with 6 100 watt panels. Now the panels are all hqst 100 watt, but 2 of them are a year older than the others. And they are different. Until this point no problem they usually produce around 32 33 amps in good sun, I'm happy with that. I have them hooked up two strings of three in series and the 2 strings hooked together in parallel. Untill yesterday everything was fine but now in full sun close to midday they only produce 18 amps. I unhooked the two older panels and just ran the newer 4 and produced 23 amps so i assume something is up with the older panels. They look fine no visible damage there as clean as the other ones. These older panels are a touch over 4 years old so not old. Any ideas of the issue here? And just so you know if you're too technical its going to fly over my head speak to me like I'm ten or so haha

 

[Mattb4]

Check the voltage of the 2 older panels with a meter while they are in the sun but not connected to anything. They should read close to Voc. You can also do an amperage check if you know how to hook up your meter. Many DMM's allows up to 10a and a 100w panel is likely around ~6a Isc.

One thing to also check is your MC4 connectors. A bad connection will effect panel production.

 

[Rednecktek]

What charge controller are you using? Do you have a breaker or disconnect on your PV line you can "reset" your panels and see if the SCC starts doing more?

 

[chrisski]

At least you isolated it to the panels where at least one is bad.

Recommend checking connections. I've found many a screw that has backed itself off or the wire has settled and this effects the output.

After you check connections you may be able to switch one of the new panels with one of the old ones and see what happens. Repeat. If one is significantly less output than the other, that points to it being bad.

 

[Rednecktek]

+1 to flakey/dirty MC4 connector. Check voltages between strings to make sure they're close to each other.

 

[Prettyaimless]

I checked the voltage of all the panels and they are pretty much all the same. How do you clean a mc4 connector?

 

[Rednecktek]

PLASTIC SAFE spray electrical cleaner. Best done at night.

Yes, there is a difference.

 

[chrisski]

I used acid brushes and isopropyl alcohol to clean connectors.

 

[Prettyaimless]

Thanks for all the replies. It was a dirty connection. This is a learn as you go thing. Again thanks to you all.