question

river avatar image
river asked

250/100 MPPT pv strings

I have an MPPT 250/100 mc4 and 48v battery bank. I have 8 x 325 watt 12v panels. Can I have just one string of 8 in series or should I have two strings of four, each connected independently to a positive and negative plug on the MPPT. In the 2 string option, does this make the array a series parallel connection as the plugs are bussed together inside? Would I need to put breakers on the two strings?

MPPT Controllers
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1 Answer
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klim8skeptic answered ·

You should probably use the Victron online MPPT calculator.

parallel connection .... Would I need to put breakers on the two strings?

Without panel specs, I would guess that 2 strings paralleled would be over the MC4 connector limit of 30a.

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river avatar image river commented ·
Thanks. But would the 8 in series be the correct option?
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klim8skeptic avatar image klim8skeptic ♦ river commented ·

Need_panel_specs...

Or a data sheet, or even a web link..

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river avatar image river klim8skeptic ♦ commented ·

Below is all the info I have on the panels


325 watt panel

open circuit voltage 21.6v,

max power tolerance +- 3%

max power voltage 18v

max system voltage 1000v

cell tech, mono

18 amps

operating temp min -40 c

operating temp max 85 c

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klim8skeptic avatar image klim8skeptic ♦ river commented ·

You are all good for a single string of 8 panels.

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river avatar image river klim8skeptic ♦ commented ·

Thanks. I owe you a beer

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river avatar image river klim8skeptic ♦ commented ·
Thanks again for your help. One more question please, if you don't mind. The MPPT 250/100mc4 data sheet says max pv short circuit 70 amps (max 30 amps per mc4 connecter). Does that mean I can have 2 or 3 20amp strings connected to the controller provided the voltage is not higher than 250V?
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klim8skeptic avatar image klim8skeptic ♦ river commented ·

Does that mean I can have 2 or 3 20amp strings connected to the controller provided the voltage is not higher than 250V?

Correct.

Bad things happen if you exceed the mppt's input ratings.

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