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cstan22 · 02-06-2019, 07:36

I have two solar panels, 100w poly and 160w mono, connected in parallel, connected to a Votronic MPPT controller with a 40 amp fuse. Separately, i have three 100w monos connected in parallel and also connected to the same Votronic MPPT controller.

I unplugged the new 160w panel last night to put it away while we're going to be away for 2 months. Then I stupidly connected the loose cables, putting the system in series (I guess?), and breaking the fuse in the Votronic the next morning.

I replaced the fuse, and the Votronic started reading amperage from the three 100 w panels. I disconnected them. I re-connected the 100w poly. It shows a proper volt reading but no amps. I used a multimeter to check the voltage along the system, first checking at panels, then at each connection, and all the way to the Votronic.

I reconnected the 160w mono to the parallel circuit with the poly and I have current again. Weirdly, my battery control system is reading a higher input current to the batteries than the solar is providing (there's nothing else adding current...)

How can I have a volt reading from the poly panel and no current? Did I damage it when I connected the system in series? How can my BCS show a higher current than I'm generating? Is the Votronic somehow now miscalibrated so that it's only not showing current from the poly panel even though there is some?

Thanks for your help!

DeepFrz · 02-06-2019, 08:11

What is the minimum voltage required by your MPPT controller? Perhaps you are not exceeding that value with just the 100w poly connected?

smac999 · 02-06-2019, 08:12

Why do you have so many different panels connected To to the same controller? They should be indentical.

cstan22 · 02-06-2019, 08:43

Not sure how to tell. It's a Votronic 420 Duo Digital. User manual says Max volts are 50 V. Says for a 12 V system, the VoC should be between 20 and 23 V. Is that the number you're asking about?

The three 100 W and the 160 W all say ~21 V on the multimeter. The poly panel only reads ~16 V. There used to be two of the same of the 100 W poly panels, but one stopped showing any voltage, so I assumed it was dead and purchased the 160 W mono as a replacement. All of these came from the previous owner.

I've tested it before, where I disconnected all but the 100 W poly panel, and it produced a couple amps at least. The 100 W panels produce about 6 amps each. Has having it in parallel with the 160 W panel affected it somehow?

ohgary · 02-06-2019, 09:01

Your going to need a load to read current. Are your batteries already fully topped off? Is your charger working?

john61ct · 02-06-2019, 09:03

First off, yes, all panels connected to a given SC should ideally be identical.

It is very common for a faulty or damaged panel to show voltage at an open circuit, but unable to produce significant power (watts, amps).

There are many possible causes.

Test panels with another SC and independent known-good instruments, setting that SC aside.

Then test the suspect SC with known-good panels.

**GordMay** · 02-06-2019, 09:09

Quote:

Originally Posted by ohgary

Your going to need a load to read current. Are your batteries already fully topped off? Is your charger working?

Indeed.
And you can read an Open Circuit Voltage, even with no load connected, and therefor, no current flowing.

cstan22 · 02-06-2019, 09:14

Why do they need to be identical?

The solar controller is working fine. Already tested with other panels.

Would the panel have become damaged when I connected the leads for the panel I removed (when the fuse blew)? I also read somewhere else that a guy had discovered that it was a problem with the MC4 connectors. But why would there be volts at all these points if they aren't working?

I need to replace the 10a fuse in my multimeter, but I'm not sure what it's going to tell me because my solar controller (which works) already tells me no amps.

Another piece to the puzzle: The solar controller is supposed to have a 40a fuse. We are leaving tomorrow for 2 months, and I don't want to come back to dead batteries, so I borrowed a 15a fuse from a neighbor and planned to only run one panel, for 6 amps at most. Could that be having an effect on the poly panel current? It doesn't seem to be affecting the other panels.

john61ct · 02-06-2019, 09:44

Quote:

Originally Posted by cstan22

Why do they need to be identical?

They don't.

Only if you care about extracting the panel output efficiently, maximizing power actually getting to the bank.

If you don't care about that, just buy $40 PWM SCs.

> But why would there be volts at all these points if they aren't working?

Again, voltage is no indicator of "working" other than wiring continuity, and should use resistance for such tests anyway.

Power output is what counts.

WRT keeping a full bank topped up, a cheap 30-50W setup at low Float V will be enough for that.

cstan22 · 02-06-2019, 09:59

Gord - there is a load connected: the batteries. And the Votronic MPPT is the amp reader. It reads, say, 6 amps from each of the working 100 W panels. But it gets nothing from the 100 W poly panel, which used to at least produce 3-4amps.

John - not sure what the takeaway is here. Based on the info I've provided, do you have a guess at what's wrong? Are there any actions I can do to isolate the issue. As in, do this, and you will know for sure the solar panel is busted, or do this and you will know for sure an MC4 connection is fried.

I understand now that trying to read current directly on the solar panel without a load isn't going to work, but again, my MPPT controller is doing just that WITH the load of the batteries, and it's returning 0amps, even though it returns appropriate amp readings for other panels.

FYI, we have 560 W of solar because we live aboard and work from our computers with the inverter. 30-50 W wouldn't cut it.

cstan22 · 02-06-2019, 10:05

WRT mixing panels - are you thinking that I'd produce more power with only the 160W 21V than with it combined with the theoretically working 100W poly?

john61ct · 02-06-2019, 11:09

Quote:

Originally Posted by cstan22

30-50 W wouldn't cut it.

That was just wrt this

Quote:

Originally Posted by cstan22

We are leaving tomorrow for 2 months, and I don't want to come back to dead batteries

> Votronic MPPT is the amp reader

I never rely exclusively on built-in meters, a known good standalone DMM + ammeter are required for troubleshooting.

Also for wiring and connectors.

My guess is the panel is broken, but I would put it on a known good SC before scrapping it.

john61ct · 02-06-2019, 11:11

Quote:

Originally Posted by cstan22

WRT mixing panels - are you thinking that I'd produce more power with only the 160W 21V than with it combined with the theoretically working 100W poly?

Easy enough to test such things, from here would just be guessing.

Note the Victron SmartSolar 75/15 are inexpensive enough, some even use one SC per panel to optimize partial shade handling.

**Jim Cate** · 02-06-2019, 15:10

I have always thought that one tested panels by exposing them to strong direct sunlight and then measuring their open circuit voltage and their short circuit amperage. If those measurements come close to the original specs, usually shown on the sticker on the back of the panel, then the panel is healthy.

This removes any consideration of the effects of load or of the functionality of a controller.

So, OP, have you done these simple tests?

Jim