Results with 2 Victron SCC MPPTs very different but why?

[WorldwideDave]

I have a 150/100 Victron connected to 2s2p 200w 25V 9A panels. It produces 5kWh of power daily. Mounted at angle of 35 degrees.

I also have another identical array 2s2p connected to a 250/70 Victron. Same panels. Produces 1.5kWh daily. Mounted flat, no angle at all, just to test.

It was time to try something else. Left old panels where they are, and I installed another array at 33 degrees of 2s2p same panels. I have 19 more panels just testing with. New wires all the way from SCC to the panels.

So far the new array is producing crap just like the old array was. Day isn’t over but I can already see this new array is putting out .4 amps while the other old one connected to the 150/100 mppt is at 2.2 amps. Voltages on both MPPTs read the same at 47.71 or so volts.

I wondered if maybe connecting four panels in series would change the output on my 250/70. It did not improve the output. I even tried adding six panels in series. The output did not improve.

About the only other test I can think of doing is to switch each string to connect to the other SCC. Another words, if the top producing string still continues to produce the most over on the 250/70, then that would rule out the MPPT being the problem.

I have read somewhere that the higher voltage MPPT’s perform better when you get them closer to what it is they expect. In other words, the 250 V one I’m running at no more than 50 V so maybe it doesn’t perform well.

If that argument were true, then over on the 150/100, I would expect to see poor results as well because the voltage never exceeds 50 V.

All panels are the same or the same vintage.

Open to any suggestions.

Shading not issue with new array.

 

[sunshine_eggo]

There must be someplace for the power to go. If your chargers are in absorption, you aren't getting the max out of the array. The chargers MUST be in bulk mode, or they are voltage limited.

Alternatively, you add loads that exceed your PV to ensure you get max PV available.

 

[WorldwideDave]

There must be someplace for the power to go. If your chargers are in absorption, you aren't getting the max out of the array. The chargers MUST be in bulk mode, or they are voltage limited.

Alternatively, you add loads that exceed your PV to ensure you get max PV available.

Right...I assure you loads are running at 70A discharge right now and battery bank nearing zero percent state of charge. MPPTs both in bulk. See below - one is at twice amps as other right now. Very strange.

 

[WorldwideDave]

Forgot I could go here too:



Look at Yield - that's awful. One is doing 32% of what the other one is doing. Makes no sense to me.

 

[Brucey]

Forgot I could go here too:

View attachment 284096

Look at Yield - that's awful. One is doing 32% of what the other one is doing. Makes no sense to me.

More than likely something wrong with one of your strings. Easy check by swapping the strings over

 

[WorldwideDave]

More than likely something wrong with one of your strings. Easy check by swapping the strings over

swapped strings from one MPPT to the other. As you can see the 250/70 is now producing more amps out.



I have a new MC4 Y adapter coming. Wondering if the one I'm using on this string is garbage.
Also could be the DC breaker
Also could be the DC disconnect.
I have spares of both of those - breaker and disconnect - perhaps I'll swap them out and see if that changes results.
The conductors are otherwise all new.
Suppose it could be a bad MC3 to MC4 adapter somewhere, but if that were true, it would also be on the other array.
Open to suggestions on the most methodical way to test.
Not super easy to get to these components with some of the wires cut-to-fit with little slack, but I can unscrew stuff and move if needed.
Happy to know it is not the most expensive part - the MPPT

 

[Brucey]

I have a new MC4 Y adapter coming. Wondering if the one I'm using on this string is garbage.

I like to use these, rated for 55A unlike the mystery Y corded splitters:

Stäubli 32.0197 MC4 Branch Connector MC4-Evo 2 Male

Shop now for Stäubli 32.0197 MC4 Branch Connector MC4-Evo 2 Male PV-AZS4-EVO 2-UR.

www.stellavolta.com

Staubli 32.0196 MC4 Branch Connector MC4-Evo 2 Female

Shop now for Staubli 32.0196 Branch Socket MC4-Evo 2 Female PV-AZB4-EVO 2-UR.

www.stellavolta.com

 

[WorldwideDave]

I like to use these, rated for 55A unlike the mystery Y corded splitters:

Stäubli 32.0197 MC4 Branch Connector MC4-Evo 2 Male

Shop now for Stäubli 32.0197 MC4 Branch Connector MC4-Evo 2 Male PV-AZS4-EVO 2-UR.

www.stellavolta.com

Staubli 32.0196 MC4 Branch Connector MC4-Evo 2 Female

Shop now for Staubli 32.0196 Branch Socket MC4-Evo 2 Female PV-AZB4-EVO 2-UR.

www.stellavolta.com

It just occurred to me that my wiring from the MPPT to the DC breaker to the PV Disconnect must be wired correctly, or else the string I just swapped would not have worked.
Basically I need to test just from the PV isolator/disconnect to the panels themselves, since it seems everything from the bus bar to the fuse to the MPPT to the DC fuse to the PV isolator all seem to be working.
That's strange though given that the other array did the same thing. Hmm.
I could try connecting the new array in 4s vs. 2s2p, but I think I had it that way before and the results were similar. That's very odd. Could also try just one pair of panels, or just one panel, or each panel one at a time - the wires are within reaching distance.

 

[Bluedog225]

I take out all those push connectors and put in butt connectors. They’re just trouble waiting to happen. Some people swear by them, though. They are particularly troublesome when they are not the same brand. And when you’re out there in the field, hooking stuff up and making things happen, often it’s hard to know what brand you’re dealing with. Unless you started from scratch. And bought all the same stuff. Even then I wouldn’t use them. I think Will Prowse has come to the same conclusion, which says a lot.

 

[WorldwideDave]

I take out all those push connectors and put in butt connectors. They’re just trouble waiting to happen. Some people swear by them, though. They are particularly troublesome when they are not the same brand. And when you’re out there in the field, hooking stuff up and making things happen, often it’s hard to know what brand you’re dealing with. Unless you started from scratch. And bought all the same stuff. Even then I wouldn’t use them. I think Will Prowse has come to the same conclusion, which says a lot.

what push connectors are you eluding to, the MC3 or MC4 connectors? My MPPTs use terminal posts, and wires run from MPPT to the PV disconnect where they have MC4 on them. But seems like that is not the issue. Out of the PV disconnect are MC4 to wires to MC4 back into DC breakers, then out as MC4 to 100' AWG 8 wires to MC4 to the MC3 to the panels. Not an uncommon setup, but heck could be bad panels. In an hour or two I'll go out, kill PV, connect one panel at a time and see if results are different between all 4 panels with same MC3 to MC4 adapters. Then I'll swap the MC3 to MC4 adapters and retest each panel. Then I'll try parallelling one pair, and testing. Then I'll try paralleling another pair and testing. Then at the very worst I will try running all in series. I can always create new MC3 to MC4 adapters.

 

[Backyard]

Take your DVM and use the DC amp setting. Measure each panels output. See if one or more has lower amps then the others. Then measure the open circuit volts of each panel.

 

[Bluedog225]

I’m not implying at all that the connectors are the issue. Simply an observation as you work on your system.

Cheers.

 

[WorldwideDave]

Take your DVM and use the DC amp setting. Measure each panels output. See if one or more has lower amps then the others. Then measure the open circuit volts of each panel.

I set up 6 panels, not connected to anything, I plugged a single one in with the same MC4 to MC3 adapters and just went down the line in a row, looking at my MPPT's output as I went. They are all very close.
Then I had a thought.
I put two panels in series, and viewed results on SCC.
I then added a third panel in series, and viewed results on SCC.
I kept going until I had 6 panels in series. The smaller 150/100 threw alert as voltage was hovering around the 150 mark, so backed off one panel. Tested for a bit. Results were about 1/3 what the other array setup in 2s3p were.
Simply switch MPPTs - put the parallel strings on the 150/100, and the series string on 250/70, and added the 6th panel back.
At 140-160 volts during the day, the series string did well.
Then I remembered - I have that other array with the panels flat, also 6 in series.
I put a MC4 branch (parallel) connector before the DC fuse, connected both strings in parallel, to run 12 panels at once - my first time - in 6s2p.
It did very well - better than the 2s3p 6 panel array.
I plan to leave it like this for a day or two - expecting rain - then report back. Because I was switching things around a lot - even moving furniture and plants to remove shading - I want to see how it does over some time.

Low producing day with rain and clouds and fog, but it is doing okay. Big consumption was me trying to draw down the battery into a low SOC so the panels could recharge; turned off the load once hit 0% SOC just to watch it charge.



Had 114+ A coming off 2 MPPTs today - that's not a record but pretty great for clouds, rain, and fog:



Also looks like the 250/70 is the one producing more now - of course it has 12 panels (6s2p) instead of 6 panels (2s3p). These aren't bad numbers:


Will see where things are in a few days.

 

[Backyard]

I set up 6 panels, not connected to anything, I plugged a single one in with the same MC4 to MC3 adapters and just went down the line in a row, looking at my MPPT's output as I went. They are all very close.
Then I had a thought.
I put two panels in series, and viewed results on SCC.
I then added a third panel in series, and viewed results on SCC.
I kept going until I had 6 panels in series. The smaller 150/100 threw alert as voltage was hovering around the 150 mark, so backed off one panel. Tested for a bit. Results were about 1/3 what the other array setup in 2s3p were.
Simply switch MPPTs - put the parallel strings on the 150/100, and the series string on 250/70, and added the 6th panel back.
At 140-160 volts during the day, the series string did well.
Then I remembered - I have that other array with the panels flat, also 6 in series.
I put a MC4 branch (parallel) connector before the DC fuse, connected both strings in parallel, to run 12 panels at once - my first time - in 6s2p.
It did very well - better than the 2s3p 6 panel array.
I plan to leave it like this for a day or two - expecting rain - then report back. Because I was switching things around a lot - even moving furniture and plants to remove shading - I want to see how it does over some time.

Low producing day with rain and clouds and fog, but it is doing okay. Big consumption was me trying to draw down the battery into a low SOC so the panels could recharge; turned off the load once hit 0% SOC just to watch it charge.

View attachment 284491

Had 114+ A coming off 2 MPPTs today - that's not a record but pretty great for clouds, rain, and fog:

View attachment 284492

Also looks like the 250/70 is the one producing more now - of course it has 12 panels (6s2p) instead of 6 panels (2s3p). These aren't bad numbers:
View attachment 284493
View attachment 284494
Will see where things are in a few days.

That's all well and good but you're going about it the long way. Just short the panels through your current measurement on your DVM. And measure the voltage of each panel. See of you have any outliers. A panel with lower output will pull down or restrict the other panels to its lower limit

 

[WorldwideDave]

That's all well and good but you're going about it the long way. Just short the panels through your current measurement on your DVM. And measure the voltage of each panel. See of you have any outliers. A panel with lower output will pull down or restrict the other panels to its lower limit

Will do. Noticing a trend. On some of the panels they must be a 'V2' or something - no indication whatsoever, but on some the backs of these mono panels have a black coating and others do not. Seems they produce about .5-1.5A more current than the others I have. Can't tell from the front or the ID panel or the barcodes on them or anything. Looks factory. Anyhow, for now, just trying to get to 100% SOC.
I have DVM and clamp meter, etc. Right now happy and will come back to this issue in a week. Will need to probably parallel some due to shading - have to see what the sun is doing with the time change; when its cloudy I can't visually see any shadows on from the plants/roof/walls etc.

 

[Backyard]

Will do. Noticing a trend. On some of the panels they must be a 'V2' or something - no indication whatsoever, but on some the backs of these mono panels have a black coating and others do not. Seems they produce about .5-1.5A more current than the others I have. Can't tell from the front or the ID panel or the barcodes on them or anything. Looks factory. Anyhow, for now, just trying to get to 100% SOC.
I have DVM and clamp meter, etc. Right now happy and will come back to this issue in a week. Will need to probably parallel some due to shading - have to see what the sun is doing with the time change; when its cloudy I can't visually see any shadows on from the plants/roof/walls etc.

Good find. Remember. All panels in series need to be the same amperage. And any strings wired in parallel with each other need to be the same voltage as the other strings. So if you end up mixing any of different specs you can get much lower performance then expected

 

[WorldwideDave]

Good find. Remember. All panels in series need to be the same amperage. And any strings wired in parallel with each other need to be the same voltage as the other strings. So if you end up mixing any of different specs you can get much lower performance then expected

I'm good - all same 12 panels in 6s2p right now, and the other array as well. All stickers/IDs/PNs match on all 28 panels. I will measure individually once it is a clear, warm day. For now, happy its better, though other than upping the voltage of the string, not sure what else could have done it.