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GRIGORIU avatar image
GRIGORIU asked

How to distribute at best the loading on the two MPPT's of a Multi 48/6000

I am installing an Off-grid system based on a Multi RS Solar 48/6000 in an isolated mountain cottage. The daily energy needs are not high but I need to plan the number of panels and the batteries for the worst case scenario in the winter.

I have two theoretical questions about the loading of the two MMPT of the multi

Q1: I would like to "catch" as much sun as possible in the winter. Beside the orientation/shading issues, Instinctively I would try to have the highest number of panels in series to have the highest voltage so the MPPT would start as early as possible (with of course taking into account maximum voltage in the cold winter and the Float voltage of the batteries). Is that right ?

If the response of Q1 is yes then

Based on the irradiation simulation data (max 750W:m2) and panels characteristics I am limited to 9 panels per string by the float voltage of the pylontech's. I plan to install max 14 to 15 panels – space issue (i.e. 15x 455 Wc = a theoretical 6400-6800 Wc)

Q2: How should I distribute at best the panels to get the max solar prod especially in less sunny period and be technically acceptable during the summer?

  • One string of 9 panels on MMPT1 (4 KWc) and 5 ( 2 kWc) on MMPT2
  • Two strings of 7 panels on each MPPT ( 3200 Wc x 2)
  • Or 9 panels on mmpt 1 and chose another type of panel with higher Voc on mppt 2 in order to get highest voltage possible ? - is that sort of mixing useful (different type of panels on each MPPT )
  • Or that kind of issue is irrelevant

Thank you in advance for your answers

mppt rs
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seb71 avatar image
seb71 answered ·

I don't understand the purpose of Q1. Using the maximum number of PV modules (panels) allowed by a certain MPPT will produce more energy than using fewer PV modules. Or maybe you meant something else.

On Q2:

You did not specify the PV modules orientation. You want all PV modules in a string to face the same way (same azimuth) and to have the same angle to horizontal. Also you do not want any shadow at all.

I would avoid purchasing different types of PV modules. If later you have a defective/damaged one (and replacements are no longer available), having a single type will be much better, because it allows more flexibility in re-arranging/re-configuring the PV arrays.

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GRIGORIU avatar image GRIGORIU commented ·

The purpose of q1 is not about the maximum energy to be produced which obviously depends on the number of modules but rather to know if in reality in low lightening conditions you will produce earlier/more energy. Because is high lightning conditions you will always produce more than you need.

Concerning R2: I agree with the module failure problem but neverthe less. theoretically which is the better solution. My way of doing is generally to make a model of the problem seek the optimum solution then adapt in practice.

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