75/15 and 2x 120W panels, confused series or parallel

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racerke600 asked Feb 28, '22

75/15 and 2x 120W panels, confused series or parallel

I have two 120 panels mounted to the roof of my california, and have a victron 75/15.
The vendor supllied two Y connectors to connect the panels in parallel.

But i'm maybe thinking of connecting them in series, this will reduce the clutter on the roof with the bulky Y connectors.

I already used the victron calculator and it seems that both would work.

However it says something about the max. number of solar cells being 108 for a 12V system.
This means that victron uses 36 cells panels for it's calculations?

So the main question is, can I wire the panels in series?
This would mean 144 cells?

My panels have these specs:

Generatorleistung wp	120 Wp
Solarmodul - Zellentyp	monokristalline Solarzellen
Solarmodul - Anzahl Zellen	72
Systemspannung	12 V
Zellenwirkungsgrad	18.43 %
Modulspannung (VMP)	20 V
max. Strom (IMP)	6 A
Leerlaufspannung (VOC)	24 V
Kurzschlussstrom (ISC)	6,48 A
Max. Systemspannung	200 V/DC

battery charging

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Answer 1 · 2022-02-28T11:29:23Z

wkirby answered · Feb 28, 2022 at 11:29 AM

Those specifications say that VOC is 24V, so two in series would make 48V.
The series configuration would be perfect for your 75V MPPT, in fact it would be better to use a series configuration instead of parallel.

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racerke600 commented · Feb 28, 2022 at 01:34 PM

Indeed with the VOC of 24V it seems possible. But I don't understand the limitation of the 72 cells? How does fit in the calculations?

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snoobler racerke600 commented · Feb 28, 2022 at 02:23 PM

72 cells in series.

"Split-cell" or "half-cut" panels are like two panels in parallel together in the same frame. These are typically characterized by visually having an upper and lower half with the leads in the middle of the panel:

So while it may have 72 total cells in it, it's actually 2X 36 cell panels in parallel.

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