Low amps

[Bluedog225]

I’d appreciate some help troubleshooting my very basic set up. I’m going to clean it up and redo my connections with butt once I find my stupid crimping tool.

Used panels. The mc4 connectors looked good but who knows.

I tested each of the six panels with a little solar panel tester, and they all seem to be producing within an expected ranges. I’ve hooked them up with two sets of three panels and series and I put the two strings in parallel.

Full Texas sun. Directly overhead. Cool morning. Each leg is producing 4.5 amps but each panel has an lsc of 9.26 amps.

I’ve got 9 A at the combiner box for the two strings. As expected.

This is consistent with what showing on the Cerbo.

38.7 volts with 3 in series=116.1 volts. I’ve got 90 volts. Close enough.

I’m only getting 800 watts. When the theoretical max is 6x275 is 1650 watts.

Where are my missing amps? Is this indicative of something obvious? I wouldn’t think it would be a loose connection in my series or parallel strings cause that would show up differently. Wouldn’t it? Could this be explained by a bad panel? I can take them apart and test them again.

I was curious, if there was any obvious answer to you folks were more electrically inclined.

Thanks

 

[Mattb4]

...

38.7 volts with 3 in series=116.1 volts. I’ve got 90 volts. Close enough.

I’m only getting 800 watts. When the theoretical max is 6x275 is 1650 watts.

Where are my missing amps? Is this indicative of something obvious? I wouldn’t think it would be a loose connection in my series or parallel strings cause that would show up differently. Wouldn’t it? Could this be explained by a bad panel? I can take them apart and test them again.

I was curious, if there was any obvious answer to you folks were more electrically inclined.

Thanks

Sorry but that is not close enough. I would guess that the panels are seriously aged out. I would expect at least 110Voc if they were in good condition.

 

[Bluedog225]

Good to know. Thanks.

I was thinking that 90 volts at the combiner box indicated that the panels were functional and the connections were good. Maybe not.

The panels looked like new old stock. They were stacked neatly and still had the little plastic dividers between them.

When I get back to civilization, I will check the voltage drop on my roughly 30 feet of 10 AWG THHN that’s connecting the panels to the system.

Can I poor or loose connection result in a voltage drop?

 

[Bluedog225]

Well. I see that poor connections could be the issue.

At least one of the mc4’s needs to be replaced.

It seems important to me that both strings are behaving identically. That makes me think this is not a wiring issue.

Are wire nuts ok to use on 10 awg DC wiring? Or is there a better way to combine 3 wires in a junction box? I am running 2 strings at present so no fuses or proper combiner box.

What’s the right way to do this?

 

[time2roll]

Consider removing one panel and check Isc direct with a separate meter.

 

[meetyg]

Could also be bad bypass diodes.
Unfortunately there isn't an easy way to check them without opening the junction box on the back of the panels. These are usually glued shut, so you might have to pry them open, causing unwanted damage.

 

[Bluedog225]

Well shoot. There are all pretty similar. This is the worse. When I tested him, I was attributing these readings to not having good enough sun. I guess that’s not the case.

Works this reading, on all 6 panels, be indicative of a bypass diode issue?

Beginning to rethink my campaign of buying used panels.



View attachment 216368

 

[Bluedog225]

Well. Pulled them apart and tested one at random. Near “ perfect” sun. Got good results.

I guess I’ll come back in out here some morning and pull them all apart and test them all again individually. And then do a better job putting them back together with proper butt slices and see what happens.

I need to set up some kind of testing area where I can stay in the shade and just set the panels out. Squatting down over these racks and the sun is no fun.

 

[seneysolar]

Are your batteries low enough for the CC to draw the amps? The CC will only draw what it needs and might taper off as the batteries get full.

I would only expect peak current below 80% state of charge in most cases.

Also STC panel ratings are rarely achieved. Perfect lab conditions are needed.

 

[Bluedog225]

Good point. I ran my batteries down to 50% before I hooked these panels up only getting about 800 watts from the whole array.

Given the one random panel, I tested, looked good. I guess I’ve got a bad panel(s) on each string?

 

[seneysolar]

What charge controller do you have? Battery voltage?

 

[Bluedog225]

It’s a victron 150/35 on a 48 volt SOK rack.

 

[Texas-Mark]

I would guess that the panels are seriously aged out.

Looks like they are only 11 years old. I have some that are nearing 20, and still at over 95%.

I would check each panel individually and then look at connections.

I have one of those panel test meters, but it has a voltage limit of around 70V

 

[Bluedog225]

Yeah. I’m going to build a couple of tall sawhorses and stick some 2x4’s on top. I need to do a better job testing these in full sun prior to assembling the array. That will give me some shade under while I work and I won’t’ have to work on the ground.