solar system catastrophe and rebuild

[Mike90250]

When the MC4 connectors are disconnected under a load, the resulting arc will damage the contacts and ruin the connector. 1x is all that's needed. The contacts we never deigned or intended to operate under load, and good practice dictates that systems be powered off when changes are being made. If you had a DC disconnect at the combiner box or charge controller, you don't have to cover panels.
If you have a combiner box, you can do most troubleshooting from there. (I have 5 strings on my system, and I can switch 1 on at a time and measure it and compare against it's brothers and get an instant verification they all are working)

The other issue, is naive users attempting to engineer and diagnose a system they have no background in. This leads to damaged connectors that can/will overheat on your roof, and then the pitchforks and torches come out (thank you Mary Shelly) and the revolt against the "fraud solar stuff" begins.

But this not what we want to see. Get the Dummies Handbook for Solar, either print from the bookstore, or an online download. Read it. Lean the basics, which are way too much for you to trust "strangers on the internet" and too complicated to provide electricity lessons on the internet from this forum.

[Jayson]

Great Info Mike. I do have a couple solar reference books and have been researching/experimenting with this for quite a while, so not totally in the dark.

I have only the 2 leads coming in on 10ga wire. These go to a DIN rail style breaker. The exit is 6ga wire to the controller pv input. As long as everything "downstream” of the breaker is shut off, am I okay with disconnects? The warning on the panel junction boxes and connectors has confused me about being "under load". Not sure if the sun creating juice in the wires counts as a "load".

[J.P.M.]

Great Info Mike. I do have a couple solar reference books and have been researching/experimenting with this for quite a while, so not totally in the dark.

What titles do you have ?

[Jayson]

Junior Member, Noob, Destroyer of Panels.

Oh those titles...

Mobile solar power made easy

Off-grid solar power simplified

I also have Kindle so access to lots of other titles.

[Mike90250]

In a series circuit, opening the circuit in one location, stops current flow. Then it's safe to de-mate and mate the connectors. They are still LIVE with power, but with no flow, there is no destructive arc.

Another simpler measurement, is, while the system is running, measure the PV voltage at the controller input, which should be close to the Vmp of your panels in series, if so, that's a quick check that the MPPT is at least keeping the panels at their Vmp. If you read a voltage close to battery voltage (27v) on the PV side of the controller, you have a problem

[J.P.M.]

Junior Member, Noob, Destroyer of Panels.

Oh those titles...

Mobile solar power made easy

Off-grid solar power simplified

I also have Kindle so access to lots of other titles.

Thank you.
J.P.M.

[Jayson]

In a series circuit, opening the circuit in one location, stops current flow. Then it's safe to de-mate and mate the connectors. They are still LIVE with power, but with no flow, there is no destructive arc.

Another simpler measurement, is, while the system is running, measure the PV voltage at the controller input, which should be close to the Vmp of your panels in series, if so, that's a quick check that the MPPT is at least keeping the panels at their Vmp. If you read a voltage close to battery voltage (27v) on the PV side of the controller, you have a problem

The first part "series circuit" didn't compute for me as far as where to disconnect because the 2 series groups are connected in parallel to the next series group of 2. Trying not to fry anything...where can I disconnect to achieve this or can I just shut off the breaker and disconnect one line?

Having difficulty completing the panel by panel current testing due to insane winds. Soon though...

The second part I did. Tested the pv leads where they enter the controller and found 41v.

[Mike90250]

You have 2 series circuits, each must be broken individually. Or you can use a clip on amp meter to insure they both are contributing the same amps.

With 41V at the PV side, if that's close to 2x Vmp, I'd say things are working right. if it's more than 2 volts from Vmp, it's either a really hot day, or there is a problem.

[Jayson]

Good morning. Finally a windless beautiful day, was able to complete first current test on individual panels. There is a slight variance between the right and left side I am attributing to sun angle/desert dust.... Àll panels tested between 3.4 and 3.8 amps.

10am front right 3.8 rear right 3.8
front left 3.4 rear left 3.4

I wish it was higher similar to my initial 5.7 readings at install. I will test again at 1 and 4ish. I have noticed a pattern of the highest charging (incoming wattage) happening in the mornings, but I'm not sure if that is due to the lowest battery level after running early morning loads. Hopefully getting this figured out slowly but surely! Thanks for all your help.

Does any of this testing indicate a condition in the array? Are these numbers typical?

[Jayson]

2:00 pm test

Right side producing 5 amps. Left side 4.75 amps.

My roof is slightly curved so this variance seems normal due to angling. Maybe not.

So is this pointing to something in the connections or does everything seem correct?. Going to reconnect everything and test again with the bayite amp meter on the incoming positive.

According to my limited wiring knowledge, with each panel reading ~5 amps shouldn't I be producing ~40 volts at ~10 amps with my wiring configuration?

41 volts from the series connections and 10 amps from them being paralleled together? Looks right on paper anyway.

Please help me figure out the next step or diagnose the current loss. Thank you.

[Jayson]

3:00 full test. Holding steady at 180w pv input. Between 6 and 7 amps at ~35v. Everything is humming along but I think I'm losing a connection somewhere.

It's pretty hot today, the panels are hot. They're also in need of a wash. Low on water!

One variable left to consider are the parallel connections. I used Branch connnectors (y) to join both series groups together and provide the single out to the controller. I assumed these are just a junction but maybe they are directional (as in, the 2 have to go out to the 1)?

Kinda lost as how to proceed. I should be seeing more available amps. The mppt seems to be displaying all stats correctly as does the bayite amp meter.

[Bala]

As Mike mentioned in an earlier post ensure you check anything posted by faceless internet people. With that said here is my take.

Series panels are the same as series batteries. V doubles A stays the same.

You 3Pm sun angle is similar to your 10am angle so you could expect similar results.

That would suggest you are getting as good as you can from your system.

You will get more from a better sun angle at 2pm and noon etc, as your results show.

You will lose from different angle on the roof between sides as your results show.

You will lose from heat. My panels will still give me 60A at times but at 1pm on a hot day the most I can get is 40A.

[Jayson]

Hi Bala, thanks.

Yep I'm right with ya on the math except that the 2 series groups are connected in parallel. I doubled my voltage (20 x 2) in 2 series groups to produce ~41 volts. Then with these connected in parallel shouldn't the amperage double?

[Bala]

You panels are 8.6A in a perfect world, so 2 in series will at best give you 8.6A.

You listed 3.4A and 3.8A in your 10am test, from each panel, so in series you would be seeing 3.4A from one pair and 3.8A from the other pair.

So that is 7.2 A maximum from the system at that time which is basically your 6 to 7 A you said your were getting at 3pm.

Have I got that correct????????

[Mike90250]

I'd say both strings are close enough that they are good. variations such as dirt, or some being hotter than others may explain the slight difference. Overall, the arrays are close to identical and I wouldnt loose sleep over it. Record the numbers and use to compare against the next time you test