Odd Solar Panel connection suggested by peer

[Pandemoniumppk]

This is my first system so please go easy on me. My Dad ordered the SGR-13KM Solar Kit from SunGoldPower.com with 14 solar panels and my cousin suggested we hook up the panels in a way that will give us the best of both worlds, high voltage and high amperage. The more I think about the way he explained it, and with all the research I've done, I think it's wrong. Picture 2 rows of 7 panels and numbering them 1-14 starting at the top left, working your way across the top row of 7 and then the first panel on the second row is number 8, all the way to 14. So he says we can take the - from panel 1 and hook to the + of panel 2 to achieve a 48v group in series. The + from panel 1 would go to the inverter and all the other panels would be wired in parallel like this:
the - from p2 to the - of p3
the + from p3 to the + of p4
the - from p3 to the - of p4
the + from p4 to the + of p5 and so on.

Lastly we would end up with the - on p14 being the connection to the inverter. He says this is how we can achieve 48v (peaking around 63v) and 172.9 amps (13.3 amps x 13 panels (1 group of 2) in parallel)

It seems off to hook up panels where most of them are at 24v and only 2 are running at 48v.

My research says that we could do groups of 2 in series, having each group running at 48v and then parallel these all together and achieve 93.1 amps (7 panels x 13.3 amps).

Hopefully I have supplied enough information to answer this one question. Will his way blow up or cause problems? Is my way better and closer to how you would hook up the panels if it was you?

 

[400bird]

The words you need are series and parallel.
Series is connecting the positive of one panel to the negative of the next.
Parallel is, well, parallel.

All your parallel strings must be the same voltage. You can't connect a string of 2 in parallel with a string of 4.

With 14 panels, the math says your only options are 14 in series, 2 parallel strings of 7, or 7 parallel strings of 2.

What inverter/solar charge controller are you connecting these panels to? Generally where are you located (minimum temperature is the important data point here)? And can you share the spec sheet on your panels?

 

[underdog5004]

How's he going to connect P3neg to both P2neg and P4neg?

Sounds like he's trying to make a 2s7p array, with 7 parallel pairs of series'd panels.

That would be 7x runs of wire from each pair, back to a combiner box that contains ocpd.

What's the max voc of the charge controllers input?

 

[underdog5004]

But who cares? Let the cousin fall on his face. No need to jump in.

 

[Hedges]

Difficult to figure out connections from a paragraph.
Net list would be an improvement.
Schematic is ideal.

2s7p as Underdog said is what I think you were recommending.

Me, I'd do 7s2p, because I use high voltage string inverters.

Off-Grid Solar Kit 13000W 48VDC 120V/240V LifePo4 20.48KWH Lithium Battery 14 X 415 Watts Solar Panels SGR-13KM

sungoldpower.com

90 to 390VDC is what you have to design to. I think it has two MPPT inputs.



38.82 Voc, so 7s is about 280V, right in the middle.

I'd connect 7s into one input, 7s into the other.

 

[Pandemoniumppk]

The words you need are series and parallel.
Series is connecting the positive of one panel to the negative of the next.
Parallel is, well, parallel.

All your parallel strings must be the same voltage. You can't connect a string of 2 in parallel with a string of 4.

With 14 panels, the math says your only options are 14 in series, 2 parallel strings of 7, or 7 parallel strings of 2.

What inverter/solar charge controller are you connecting these panels to? Generally where are you located (minimum temperature is the important data point here)? And can you share the spec sheet on your panels?

Yea I mostly understand series vs parallel and how the volts and amps add up. I think you answered my question with saying that all parallel strings must be the same voltage. The 3 possible ways of hooking up 14 panels that you explained lines up with the logic and research I've done. Noone is hooking up panels the way this guy is doing it and I think at the very least, it will over-work the 2 panels that are in series.

Inverter = 2 X 6500 Watt UL 1741 48V DC 120V AC Output Inverters
Location = Central Alabama

Panel Info:
Peek Power = 415w
IMP = 13.13A
VMP = 31.61V

ISC = 13.79A
VOC = 38.82V

Thank you for your response.

 

[Pandemoniumppk]

How's he going to connect P3neg to both P2neg and P4neg?

Sounds like he's trying to make a 2s7p array, with 7 parallel pairs of series'd panels.

That would be 7x runs of wire from each pair, back to a combiner box that contains ocpd.

What's the max voc of the charge controllers input?

good observation. Using splitters. Each custom made cable would have a splitter on one end.

With it all hooked up, you only end up with the Positive from p1 and the negative from p14 needing a 100ft wire going to the inverters (in my cousins model).

Max PV Mppt Operation Voltage = 90-390VDC
Max Charging Current = 120A

Thank you for your response.

 

[Pandemoniumppk]

But who cares? Let the cousin fall on his face. No need to jump in.

I do or I wouldn't have posted this question? but it's not that simple. The short answer is that I'm the guy that has 20 years of experience with technology (but none setting up solar systems) and I should have all the answers.

 

[400bird]

Hedges is right on the money. One 7s string per MPPT. You should spend some time reading the manual. I'm your first post you mentioned 170 something amps of solar input, that's not going to work and require giant cables, a combiner, etc. A single string connected to each input is right online with the recommendations that are right there in the manual.

 

[Pandemoniumppk]

Difficult to figure out connections from a paragraph.
Net list would be an improvement.
Schematic is ideal.

2s7p as Underdog said is what I think you were recommending.

Me, I'd do 7s2p, because I use high voltage string inverters.

Off-Grid Solar Kit 13000W 48VDC 120V/240V LifePo4 20.48KWH Lithium Battery 14 X 415 Watts Solar Panels SGR-13KM

sungoldpower.com

90 to 390VDC is what you have to design to. I think it has two MPPT inputs.

View attachment 169824

38.82 Voc, so 7s is about 280V, right in the middle.

I'd connect 7s into one input, 7s into the other.

View attachment 169825

Yea sorry I thought it would be better than my chicken scratch on a piece of paper, but i give in. I have even more questions now that I see it on paper.

Would your advice change knowing that It's going to 2 inverters? Wouldn't the 7s2p configuration have an amperage of only 26.26 and the little i know about home electrical wiring, that seems very low?

 

[Pandemoniumppk]

Hedges is right on the money. One 7s string per MPPT. You should spend some time reading the manual. I'm your first post you mentioned 170 something amps of solar input, that's not going to work and require giant cables, a combiner, etc. A single string connected to each input is right online with the recommendations that are right there in the manual.

View attachment 169834

Thank you for confirming what Hedges said. Yea I think I just did things out of order. I started in the manual and none of it made sense. Then my cousin gave his recommendation, then I researched, and now I posted. I should have went back to the manual but not sure that it would have totally sunk in without y'all telling me that it is correct so thank you for that.

 

[Hedges]

Yea sorry I thought it would be better than my chicken scratch on a piece of paper, but i give in. I have even more questions now that I see it on paper.

Would your advice change knowing that It's going to 2 inverters? Wouldn't the 7s2p configuration have an amperage of only 26.26 and the little i know about home electrical wiring, that seems very low?

The lower the better. Same watts, fewer amps, less energy lost in a given gauge wire.

Within limits. There is some voltage into MPPT which allows highest efficiency, and that also means electronics operates cooler.

If you have two inverters, each with its own MPPT, then could be 7s into each. The data sheet I saw indicated two inputs, so I said 7s into each input.

Looks like the bundle includes two, 6500W inverters and each has two PV inputs. Each can charge battery at 120A, 6000W or so.
6kW of panels. 4 batteries able to charge up to 5kW or so each, 20kW total.

Have you done a power audit, know what your kWh/day consumption is?

Looks like system could support twice as much PV, depending on architecture maybe more to make AC at the same time.