Series Vs. Parralel Solar Panel Wiring

Discussion in 'Off Grid Living' started by Nadja, Aug 1, 2012.

  1. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Here is the question for you. What advantage on incoming solar power is series wiring of panels vs. parralel wiring of the same panels, providing you are using an mppt charge controler like my outback mx60 ?
  2. TnAndy

    TnAndy Senior Member Founding Member

    1. If you're using a combiner box up near the panels, it takes less circuits on series strings over running each panel to a breaker in the combiner.

    2. Higher voltage means less voltage drop over the same distance. Running a 35v set of panels in parallel, all the voltage is 35. Run the same panels in series strings of 3 (105v), which an MX60 will handle with ease ( 150v input limit ), and run the numbers on a voltage drop calculator, and you'll find less drop with the same wire size from the combiner point to the CC....or you may be able to drop wire size some.

    3. The reverse is true with amps. Run 9 panels with a 7amp rating, in parallel, and you have 63amp from the combiner box ( and you'll have to buy a 12 circuit box in Midnite brand ) the same 9 panels in strings of 3, you'll have 21 amps ( and only need a 3 circuit Midnite combiner box ).
    Lot of difference ($) in the wire size for 63 amps versus 21 amps.

    NOW, let me "axe" you:

    What are the disadvantages !
    Nadja likes this.
  3. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Thanks Andy. I am only running those two 24v panels which are right at 200 watts ea straight into the mx60 which is all that is connected to it. Remember, the rest of my system is all 12v and all into C-60 charge controllers. I have just never done a multi volt system before, and wante to find out if there were any bonus's by running them either / or. I am running 8 ga wire for the two panels and nothing Else. A friend , when going out of business gave me large spools of wire, including two rolls of number 4, so wire is not an issue for me.
  4. BTPost

    BTPost Stumpy Old Fart,Deadman Walking, Snow Monkey Moderator

    The disadvantage of Series String solar Panels is:
    1. If ANY of the panels get shading it cuts the current available from that string to only the amount of the current passed by the shaded panel.
    2. Series Panels have a bigger voltage swing, from Full Sun, to Limited Sun, and that needs to be considered in the design, and choice, of the Charge Controller. Max Unloaded Voltage needs to be accounted for....
    Nadja likes this.
  5. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Didn't realize that there was a diffrence in the shading venue. Will take that into consideration. I think I will change my wiring to go in series !
  6. TnAndy

    TnAndy Senior Member Founding Member

    Bingo Bruce......any shading on ONE panel affects the total output of the WHOLE STRING in a series setup.

    Also, when you "daisy chain" the connections together, if you get some corrosion in the connection point, or any other problem with the connection ( like simply a loose connection ), you can have a whole string go dead. Had this very issue with some of the MC type connectors they use on panels now.

    And the only way I knew was I had two arrays of the same panel size, and a charge controller for each, and one day, one controller was reading 300 less watts than the other, with all other things equal ( same sun, same angle, etc ). Otherwise, with a single controller, I probably would have never picked up on it.
    Nadja and BTPost like this.
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