Overvoltage and different panels

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Andrew asked Jun 24, '23

Overvoltage and different panels

Using victron spreadsheet to calculate mppt and panels is fine, it oks 2 strings for the easy solar 48v 3kw 250/70mppt (40a ac out)

ALL 10 are 15 deg elevation south facing no shading next to each other on a wood structure 7ft high.

2 strings: 1 = 3 longi (below) and 2 JA, then nearest to house 5 x JA panels (below)

I am told by some that I need 2 x mppt and some that this is fine, sure i will lose 70w.

Is the MPPT dual as I am thinking it is overvoltage if 2 strings in series are additive? Or is it that the connection of the two strings is parallel which means not additive voltage? (string 1 is 200v and 2 is 200v surely it is 400v @ 20a approx)

Should i put 2 in parallel on each string to compensate some wattage loss?

JA = 7 @ 380w

isc 11.47a / voc 41.62

Longi 3 @ 370w

voc 40.9v / isc 11.52a

MPPT Controllers overvoltage

2 |3000

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Answer 1 · 2023-06-24T11:52:02Z

JohnC answered · Jun 24, 2023 at 11:52 AM

Hi @Andrew

The panel specs are close enough to consider them the same, so they could be wired just like you first described. Vmp isn't quoted, but should be similar to each other too.

Parallel strings don't add V, but the Current is additive. So you'd have like 200V (less for Vmp) @ 23A.

You won't lose much power doing this, and you could even test it if you had separate isolators on each string. Don't muck with parallel panels within strings, that will only hinder.

2 |3000

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