3 solar panels in series or parallel?

DIY
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1

I have three REC 330 NP solar panels. Here are the specs.

330 watts

Rated v VMPP 34.6

Rated current Impp 9.55 a

Open circuit current Isc 10.33a

I did the calculation of 990w/12v= 82.5a

So I think I need a 150/85 MPPT controller to run all three panels in series but is there a way I can run two panels in series and the third one in parallel and get by with a smaller controller? If so what size?

Is there a problem with doing that or any reason not too?

Thank you for any tips or suggestions.

What size controller would work on just two of the above mentioned panels.

These are going on a cargo trailer conversion. As of right now I only have one SOK 12v 100 AH lithium battery but I plan to add at least one more and maybe two more.

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2

This is what you will want to use.

3

No, both because series/parallel strings need to be balanced, but also because the wattage is the same regardless of if they’re in series or parallel.

Coupla things, though:

  1. You could put two in series on one controller, and the 3rd on a totally separate controller. Both controllers would then be smaller. VOC of those panels is 41v, so you could put two in series on a 100/50 and the 3rd panel on a 100/30 if you wanted. Not sure if that’d be saving any money really though.
  2. You don’t charge a 12vNom battery at 12v, so realistically you could easily get away with a single 150/70 with all 3 in series.
4

Not quite. The math works more like this. 990W / 14.4(charging voltage) = 68.75. But use the MPPT calculator. It will allow you to factor in all the details and get you closer to what you need.

Not sure what you mean by two in series one in parallel. If you mean two in series and one by itself then that would work with two separate controllers. This isn’t a bad idea especially if the series panels are on one side and the single panel on the other side. If one array is shaded, or the panels are at different angles the other side will work independently.

5

Looks like you clicked “Reply” right before me. Glad to see we are on a similar page.

6

Ah, yes, I don’t know what I was thinking. Your right, the lithium battery is 14.4v, not 12v.

Sounds like a single 150/70 controller will work. I’m in S. Az so I don’t expect to see too many really cold days when the panels are producing higher than normal power.