Solar Panels with different outputs.

[Jeffz]

Can you combined solar panels with different output watts, voltage, and current?

 

[ricardocello]

Combining panels in series with different Imp (max power-point current) will limit you to the lowest current panel.
This is not desirable.

Combining panels in series with different Vmp (max power-point voltage) is ok (as long as the voltages aren’t too far off to cause damage).
The voltages add.

Combining panels in parallel with different Imp is ok, currents will add if the voltages are close.

Combining panels in parallel with very different Vmp (> 5%) should be avoided because the MPPT voltage selected will be sub-optimal.

Similar answers for Isc (short circuit current), and Voc (open circuit voltage).

 

[Jeffz]

Thank you.

 

[CaliSunHarvester]

Combining panels in series with different Imp (max power-point current) will limit you to the lowest current panel.
This is not desirable.

Combining panels in series with different Vmp (max power-point voltage) is ok (as long as the voltages aren’t too far off to cause damage).
The voltages add.

Combining panels in parallel with different Imp is ok, currents will add if the voltages are close.

Combining panels in parallel with very different Vmp (> 5%) should be avoided because the MPPT voltage selected will be sub-optimal.

Similar answers for Isc (short circuit current), and Voc (open circuit voltage).

I have 11 panels of 355W (Vmpp = 34.7V, Imp = 10.25A) left over.
And also 9 panels of 425W (Vmpp = 72.9V, Imp = 5.83A).

Could I take 10 of the first and parallel them with 5 of the second?
First string would be 347V and second string 364.5V

364.5 / 347 = 1.0504 so just at your 5% rule of thumb.

Since the Vmpp is so drastically different, I don't think I can combine them in one string.

as long as the voltages aren’t too far off to cause damage

what damage exactly could or would happen if I were to combine 3 panels with Vmpp 72.V and 3 with Vmpp = 34.7V?
I assume the damage would be to the lower voltage panel?

Surprisingly, the 355W panels have a max string voltage of 1000V and the 425W panels a max string voltage of 600V.

 

[ricardocello]

I have 11 panels of 355W (Vmpp = 34.7V, Imp = 10.25A) left over.
And also 9 panels of 425W (Vmpp = 72.9V, Imp = 5.83A).

Wow, 72.9V is really high!

Could I take 10 of the first and parallel them with 5 of the second?
First string would be 347V and second string 364.5V
364.5 / 347 = 1.0504 so just at your 5% rule of thumb.

Would probably be ok. My combinations have always been less than 2%, so I can’t say for sure.
It would be interesting the see where the maximum power point voltage actually settles between 347 and 365.

Since the Vmpp is so drastically different, I don't think I can combine them in one string.

I’d be concerned, maybe others here have done it.
It is a bad idea because the Imp of the string will be limited by the lower current panels, not worth it.

what damage exactly could or would happen if I were to combine 3 panels with Vmpp 72.V and 3 with Vmpp = 34.7V?
I assume the damage would be to the lower voltage panel?

I think it would be the excess current going through the bypass diodes on the higher voltage panel if it is badly shaded.
They are designed to handle the normal amount of current, which is about half of the rating.
I’m definitely not the expert here, see if others have a better opinion.

Surprisingly, the 355W panels have a max string voltage of 1000V and the 425W panels a max string voltage of 600V.

600V system voltage for residential, 1000V system voltage for commercial.

 

[J.H.]

Thank you.

I was sorta in the same boat sorta as panels change through the years …….I chose to just go with a different SCC for each group of different panels and join them at my bussbars..that way they are all converted by the SCC to the proper programmed setting to work with each other…

But then maybe that’s just my way…I’m sure there are other ways ..

Good luck ….J

 

[chrisski]

have 11 panels of 355W (Vmpp = 34.7V, Imp = 10.25A) left over.
And also 9 panels of 425W (Vmpp = 72.9V, Imp = 5.83A).

Could I take 10 of the first and parallel them with 5 of the second?
First string would be 347V and second string 364.5V

364.5 / 347 = 1.0504 so just at your 5% rule of thumb.

Since the Vmpp is so drastically different, I don't think I can combine them in one string.

In my signature block, there’s a link to mixing and matching panels that will give you an idea of loss with math to back it up. Also goes over series, parallel, and series/parallel combinations.

 

[CaliSunHarvester]

I was sorta in the same boat sorta as panels change through the years …….I chose to just go with a different SCC for each group of different panels and join them at my bussbars

Yeah that would obviously work, but I am too lazy to run more wires (I already have some of them installed and looking to add to that string).

 

[CaliSunHarvester]

600V system voltage for residential, 1000V system voltage for commercial.

Except that the 425W panel with the 600V limit is marketed as "commercial":

21-Pack 425W SunPower Maxeon Used Panels - 8.9kW Pallet (SPR-425E-WHT-

This pallet includes 21 SunPower Maxeon 425W solar panels, model SPR-425E-WHT-D, totaling 8.9 kW. These panels feature SunPower’s signature Maxeon Gen 3 cell technology, which uses a copper-backed design to deliver industry-leading efficiency, extremely low degradation, and excellent durability...

clearenergypartners.store

 

[J.H.]

Yeah that would obviously work, but I am too lazy to run more wires (I already have some of them installed and looking to add to that string).

Yea your right about efforts plus it cost more…but after yer done it does work well…plus if a CC goes south or a tree falls on it you can isolate it with a MRCB. without messing with other arrays…

plus ya get more power as ya don’t have to have all the panels all at the same direction and slant as with one CC….I’m sure there are other good reason for or against , but they elude me.

Not right or wrong ,just a different way…that’s just what I do…

plus all the blue boxes and lights look cool on the wall ….
…..J

 

[CaliSunHarvester]

In my signature block, there’s a link to mixing and matching panels

Good article, I finally tried it out with my numbers. Thank you