question

wolfbarnsolar avatar image
wolfbarnsolar asked

MPPT 250/100 250w upgrade to 405w panels

currently running 16x250w panels in 4 strings

to update the panels to 405w i calculate I can only have 12 panels in 2 strings as to not overload the controller

are my calcs correct ?

MPPT Controllers
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3 Answers
Duivert NL avatar image
Duivert NL answered ·

Without specs there is nothing to say about it..

You can use the mppt calculator


https://www.victronenergy.com/mppt-calculator

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Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

wolfbarnsolar avatar image
wolfbarnsolar answered ·
2 comments
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image kevgermany ♦♦ commented ·
You need to select custom module, then put in the full panel specs.
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wolfbarnsolar avatar image wolfbarnsolar kevgermany ♦♦ commented ·
Ok great thanks
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wolfbarnsolar avatar image
wolfbarnsolar answered ·

Made no difference at all inputting custom panels info 250/85 108% oversized recomended 250/100 still 91% undersized

4 comments
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image kevgermany ♦♦ commented ·
Sorry, I was expecting a difference. How are you getting the oversize undersized values?

But the calculator will allow a 130% oversize if you tick the box. Most of the day the sun is at a lower than optimal angle and there's a relatively short period when you can use max power. In many parts of the world panels rarely output the rated power.

But doesn't matter. As long as the calculator doesn't object, using a bigger controller does not affect performance, just costs more and gives you more headroom.


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wolfbarnsolar avatar image wolfbarnsolar kevgermany ♦♦ commented ·

Ok so if its Telling me its 91% Undersized thats no reflection on performance or un-suitability just that its only using 91% of its capability so is Fine to use

as opposed to 108% oversize is over its capability but within 130% of victrons Design parameters.

The main thing is that Either is controller is acceptable & I have 2 x 250/100 controllers on my current system I can utilise for the upgrade

Note: I would have thought the 250/100 should have been the 1st/better option in the calcs /recommendation for warranty purposes not considering Price.


LOVE LONGBOATS


                   
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kevgermany avatar image kevgermany ♦♦ wolfbarnsolar commented ·
They're designed to work at full capacity

130% is a rule of thumb, as long as input voltage and short circuit current aren't exceeded you can go higher.


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wolfbarnsolar avatar image wolfbarnsolar kevgermany ♦♦ commented ·
thanks for clarification & the Education

Appreciated

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