String Design

Bendesa1962
Bendesa1962 Registered Users Posts: 5 ✭✭
in PV Installers Forum - NEC, Wiring, Installation #1

Hi Everybody,

I have the following question and would appreciate all advise and tips. Thanks in advance

I have a charge controller with the following specs:

It's the Growatt 5000 SPF Off Grid Inverter/charger

PV Array MPP voltage range                                                         60 – 115 VDC
Max PV Array open circuit voltage                                                 145 VDC
Max solar charge current                                                                70A
Number of MPP trackers / number of string per MPP tracker        2 / 1
Maximum input power                                                                    3500 Watt


PV Module Data:
250    Wp
Voc       36,5V
Vmp      30,4V
Isc         9,21A
Imp        8,22A

I want to connect 14 PV Modules of 250 Wp

How would the string design be?

Looking foreward to your reactions

Thanks in advance

Regards

​​​​​​​Johan

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Comments

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    Is the 70A the total for both inputs, or for each input? Can't seem  to find specs on the SPF, the panel count 14×250W is the maximum input wattage, but the open circuit voltage only allows 3 per string and 3 doesn't divide into 14.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Bendesa1962
    Bendesa1962 Registered Users Posts: 5 ✭✭
    #3
    Hi Mcgivor,

    Thanks for your reply. That's exactly my point. I think connecting 14 panels to this inver is not possible.

    If someone has any other ideas

    Please let me know

    Thx
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #4
    What is your system voltage? Are the 2 inputs independent?

    While they have only one input, I would think, if you have a 48 volt system, you could run 2 parallel strings into each input. The manufacturer should have some information. If they are independent you could run them without a fuse or breaker for each string, but safer just to go ahead and have a breaker for each string.

    This would still be below the 70 amp output, and unshaded strings, in parallel should not create a tracking problem. Still can't get 14 panels in there, since the VOC would be too high.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #5
    Is the MPP  70A  for both, or one input, this would be very helpful in answering questions.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #6
    Temperature at your location is also a factor. The strings need to be set up so that Voc at record low temps at your location is <145v, and Vmp at highs >60v.

    If Vmp is low with hot panels, you just won't charge. If Voc is too high though, you can damage equipment and void warranty.

    Voltage drop in the wire from array also needs to be considered.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Bowsie10
    Bowsie10 Registered Users Posts: 1 ✭
    #7
    Best configuration would be 4 strings of 3 panels. 2 strings into first MPPT and 2 into the second. 12 panels total.
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