question

ukxan avatar image
ukxan asked

Oversizing panels Easy solar 48/3000 GX 250/70

I intend to put up 2 strings of 410 w panels

Each string will be 7x410 w panels.

I have checked on the calculator and it seems I am 20 v over the limit for the rated MPPT at 130%

My question is- will that fry the MPPT or allowable as the min temp in UK in norfolk wont go down much below -7 or -8 in winters?

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marekp avatar image
marekp answered ·

You cannot have voltage from panels go over 250V at any time.

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ukxan avatar image ukxan commented ·
Many thanks, I wasnt sure 20 v above would be lethal !
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sharpener answered ·

How much temperature margin do you have i.e. using the calculator with the exact parameters for your panels at what temperature do they give you 250V on open circuit?

As I recall, 2 strings of 5 Longi 405W panels were the most I could put on a 250/70. Apart from voltage considerations 2 strings of 7 is seriously over-panelled, do you have a particular reason for this?

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ukxan avatar image ukxan commented ·
They dont but the calculator accepted 7 panels in series when the Voc was 33 v at -5c but actual Voc is 37

I bought 14 panels so was trying to see if it was feasable.

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kevgermany avatar image kevgermany ♦♦ ukxan commented ·
Trying to trick the calculator like this will result in a very expensive MPPT failure. Victron's warranty won't cover it.
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ukxan avatar image
ukxan answered ·

Thanks everyone,

Ive decided to go for the smartsolar mppt rs 450/100-tr to leave room for further expansion.

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sharpener avatar image
sharpener answered ·

<to leave room for further expansion>

50V x 100A is only 5kW.

So at 5740W the nominal output of your 14 panels is more than the max power rating of a 450/100, it will work OK but is already overpanelled.

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