Solar panel diodes - question

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  • borosane
    Junior Member
    • Jul 2014
    • 11
    #1

    Solar panel diodes - question

    Hi All,

    I just noticed i have posted my question in wrong thread, so here it is again.

    I have built my own 20V 8A - 160W monocristaline panel. Putted some bypass diodes (45V 15A schottky) between bus wires, between arrays of cells, (3 total in panel) and all flooded with silgard.
    For now, all looks fine but i have a plan to connect more panels together.

    P1010158.JPGP1010158.JPG
    P1010163.JPG

    Now, i have a plan to build/connect 8 panels in total (8 x 160W panel), and since i have already putted bypass diodes in 1st panel (45V 15A), after i connect 4 panels in parallel (32A) and then connect another array of 4 panels in series i'll have around 40V 32A total. Now to my knowledge, this is also the voltage/current that will be passing through each panel.


    MY QUESTION:
    1. What will happen with diodes from 1st panel, will the survive?
    2. Can You please recommend what kind of diodes/fuses to use as a bypass between panels ?

    I appreciate all answer.
    Thank You all very much.
    Tags: diodes solar panel
    • borosane
      Junior Member
      • Jul 2014
      • 11
      #2
      Anyone ?

        Comment

        • Mike90250
          Moderator
          • May 2009
          • 16020
          #3
          1) I don't know.

          2) never heard of diodes between panels. New to me, no comment.
          Powerfab top of pole PV mount (2) | 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

            Comment

            • inetdog
              Super Moderator
              • May 2012
              • 9909
              #4
              The bypass diodes will only conduct when part of the panel or part of the string of panels is in shade while the rest is in sun.
              Since the internal bypass diodes can all conduct if the whole panel is in shade, the only reason for external bypass diodes is to let the bypass happen with only one diode voltage drop (~.7V) instead of three (~2.1V). I know that the Schottky diode forward drop is closer to .2V, but when it is conducting close to its rated current the internal resistance will increase the voltage drop.

              As for fuses, if you have three or more strings you must put one series fuse in each string. The fuse size should carry the full string Isc, but no more than twice the string Imp.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

                Comment

                • borosane
                  Junior Member
                  • Jul 2014
                  • 11
                  #5
                  Originally posted by inetdog
                  ..the only reason for external bypass diodes is to let the bypass happen with only one diode voltage drop (~.7V) instead of three (~2.1V). I know that the Schottky diode forward drop is closer to .2V, but when it is conducting close to its rated current the internal resistance will increase the voltage drop.
                  I guess then, there's nothing gained if I bypass panel with only 1 diode, instead of 3. Thank You on clarification.

                  I'll inform myself little more about fuses. Thanks!

                    Comment

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