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upsi asked

MPPT Calculator 2s4p

Hi, I tried to use the MPPT Calculator to determine best fit for my planned strings but don't understand the max current value. Might be a simple misunderstanding on my side.

2s4p with Trina Vertex S+ 440WP

VOC= 52,2V; ISC=10,67A; VMPP=44V; IMPP=10,01A; ISC 0,04%/K and VOC=-0,24%/K

My calculation:

VOC(Max)=113,67V which is what the tool delivers as well.

ISC (Max)=46,87A but the tool delivers 78,3A and recommends a MPPT 150/70.

How can 4 parallel 10A modules deliver 78A?

What is the best MPPT if I have two 2s4p strings?

mppt calculator
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kevgermany avatar image kevgermany ♦♦ commented ·
What voltage is your battery bank?
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2 Answers
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Matthias Lange - DE answered ·

The second number of the MPPT is the max battery charging current, not the Isc.

Did you set your battery voltage?

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upsi answered ·

Yep then the value makes sense. The system voltage is set to 48V. 3520W / 48V = 73,3A plus the temperature drift may bring you to the 78A shown by the tool. Taking into account the roof faces East with 20 degree slop the maximum power will anyhow never be reached. So the 70A limitations sounds fine.

I planned to use 2x2 Pylontech US3000C. What do you think, should I go the all 4 parallel as I will use two of the 150/70 for two 2s4p strings?

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Alexandra avatar image Alexandra ♦ commented ·
Unless you have a specific reason for that many parrallel strings, I would use a 250/70 and go 4s 2p. Less less switchgear and cable bunch or gauge.
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