Wire in Series then all wired together in Parallel

ccrisham
ccrisham Registered Users Posts: 2 ✭
edited April 2022 in Caravan, Recreational Vehicle, and Marine Power Systems #1
I have a victron mppt 100/20 controller I was wondering about doing a series and parallel connection with my 200w 24v pannels

If I do just 2 in series it will be about

75V
5.4A

So was wondering could I just add a 2nd string and get

75V
11A

I dont see why it would not work but I cant find any info on anyone saying not to do it only thing people say is dont go over the max V

Thank you
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Wiring 4 panels:
    2 in series
    2 in series
      and then paralleling those 2 groups of panels to get 75V, 11A
    would be just fine for most charge controllers.   You have to verify your panels Voc when cold, would
    not exceed the max voltage input for you controller.
      Remember,  75V max power,  closer to 95V open circuit on a cool morning.   Many charge controllers
    have a sizing tool on their website, to verify you wont exceed the limits

    shorthand:   2S2P for your panel arrangement

    75V, 11A = 825 watts.   12V = 69A output from controller.  24V = 34A output

    Following screen shot shows MPPT controller converting high voltage ( 79.2v) from solar,
    to lower voltage & higher amps to the battery



    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • Photowhit
    Photowhit Solar Expert Posts: 6,017 ✭✭✭✭✭
    #3
    ccrisham said:
    I have a victron mppt 100/20 controller I was wondering about doing a series and parallel connection with my 200w 24v pannels

    Victron Charge controllers are rated at max input voltage and output amperage. So output is limited to 20 amps, if you have a string of 2 - 200 watt 24 volt nominal panels, you would have an input of 400 watts, but at 12 volt charging around 15 volts, you would have a possiblity of 400 ÷ 15 = 26.66 amps.

    So an important question is what is your system/ battery bank voltage?
    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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  • BB.
    BB. Super Moderators, Administrators Posts: 33,714 admin
    edited April 2022 #4
    Yes, it would work, but the "typical" best case charging current (a few times a year on cool/clear days around solar noon):
    • 800 Watt array * 0.77 panel+controller deratings * 1/14.5 volts charging = 42.5 Amps
    • 800 Watt array * 0.77 panel+controller deratings * 1/29.0 volts charging = 21.2 Amps
    So, with a 20 Amp MPPT controller (max output charging current)--You are losing around 1/2 of the potential array harvest on a 12 volt battery bank.

    On a 24 volt battery bank--Pretty much maxing out the 20 Amp charge controller (which is just fine--You are losing only a very small amount of total harvest).

    The present controller will work fine--But adding a second array on cool/clear days around noon--You are losing quite a bit of harvest potential. A second 20 amp controller or >~40 Amp MPPT controller would be a better fit long term.

    And as Mike says/asks... How cold of weather are you planning on... If you are in seriously cold weather (well below freezing), your array could easily exceed 100 VDC Voc-array (voltage open circuit) limit of your present charge controller.

    Need the exact Vmp/Imp/Voc/Isc of your panels and what is the minimum temperature your array is expected to experience?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ccrisham
    ccrisham Registered Users Posts: 2 ✭
    edited April 2022 #5
    Yes battery V is 24 system  and I am in central FL so temps dont get too cold.  

    I was figuring it would work fine with a 24v system 2 sets of 2 x 200W panels

    I currently only have 2 of the 200W panels but planning to get more and glad I dont need to get a 2nd controller for that set.

    Thank you for your help 

    • Maximum Power(Pmax): 200W
    • Maximum Power Voltage(Vmp): 37.6V
    • Maximum Power Current(Imp): 5.32A
    • Open Circuit Voltage(Voc): 45.4V
    • Short Circuit Current(Isc): 5.83A
    • Maximum System Voltage(Vmax): 1000V DC
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