Solar panels won’t work in series?

[Bud Martin]

At this point you have to find out why you are not getting the Voltage at the MC4 connectors end when the panels are connected in series.

 

[Thorium]

Thanks, I have new MC4 connectors coming Fri and will replace them all.

 

[sunshine]

Have you tried turning it off and on again?
With battery and everything disconnected??
Tonight have all your connections wired up and unit turned on.
Get up at sunrise and watch the PV voltage rise. If unit reads PV In ok before the PV rises above 20V and then stops at a higher voltage it is the unit at fault (or throw a blanket over panels) .

Try a 12v 20w lightbulb across the pv cables in sun and work back from there.

 

[Thorium]

Since I can’t get the expected voltage reading (only when the 2 panels are in series) with a multimeter, I’m focusing there first, not the MPP.
The MPP is aligned with the multimeter (eg one panel shows good, +20v, and the mpp solar also sees and charges off the one panel just fine).

Two additional panels I had already ordered are due for midday delivery, so I will leave those with the factory Anderson connectors these panels come with and test them as well.I also have a separate PV cable so it will be the same model of panel, also 2 of them in series, but a completely independent set of hardware.

 

[sunshine]

Two additional panels I had already ordered are due for midday delivery,

Just a question -
Why in series for a 12v system?

 

[Thorium]

The MPP solar I’m using can take 6x100 panels, but to get it in the right voltage/amp range it will need to be 3s2p.

todays tests showed measuring voltage at the MC4 with the 2 panels in series was good. The bad voltage is only when the PV wires are in the mix. The PV wire is windy nation so high quality. I did use two different brands of chinesium Amazon MC4 connectors along the way. So my next step is to replace all the MC4 connectors. I ordered some staubl authentic multi connector… I’ll report back after those come in next week.

 

[Thorium]

Logic would say it would be if both panels worked independently on the SCC, that once put in series to an MPPT rated for the voltage in series, it would work fine.

In troubleshooting though, logic is sometimes challenged with bad connections. Not all connectors are created equal and may work plugged directly to the SCC, but there’s something about the male to female connection on the panel that just isn’t working.

I’m trying to figure something like that out with my RV. I’m on my second 15 amp to 50 amp 12” connector that went bad for my trailer with the same leg of the 50 amp circuit dying. If I hook the 15’ 50 amp can;r to a 50 amp to 30 amp adapter, and then 30 amp to 15amp adapter, tI get power like I should. I don’t know what logic should tell me to do. I think I may need to replace the trailer 50 amp jack since two of the other adapters want bad.

PROBLEM SOLVED.

I think this was the winning answer.

The root cause was the MC4 connectors.
1) I had used two different budget brands of MC4 connectors from Amazon
2) pretty sure they were making some contact but really bad contact and something about the higher voltage of panels when in series made the issue present itself.

I replaced all connectors with authentic staubli multi contact connectors and all good now.

i appreciate the brain trust here Helping.

 

[12VoltInstalls]

Get the panels out of the sun
check ohms of wiring and panels. And cables alone. You might find the bad connection

 

[AlexanderKristiansen]

PROBLEM SOLVED.

I think this was the winning answer.

The root cause was the MC4 connectors.
1) I had used two different budget brands of MC4 connectors from Amazon
2) pretty sure they were making some contact but really bad contact and something about the higher voltage of panels when in series made the issue present itself.

I replaced all connectors with authentic staubli multi contact connectors and all good now.

i appreciate the brain trust here Helping.

I have exactly the same problem. Two panels each showing about 20V, connected in series 0 volt. If its ht e MC4 connectors do I have to replace all of them, or is there a way to find out which one is faulty?

 

[Thorium]

1) Carefully visually examine inside of connectors, confirm you didn’t put any male/female internals in the wrong housing.
2) process of elimination, eg connect one panel see if you issue, two panels, etc.
3) id still just replace them all if you used Chinese knock off Mc4 connectors (like most do including me until I had this problem). do so with authentic staubli mc4 connectors: https://www.ecs-ecart.com/mc4-connector.html