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GaryS1953's avatar
GaryS1953
Explorer II
Feb 12, 2018

Adding 3rd Solar Panel

Hi All - I currently have 2 12 volt 165 watt panels wired in series on the front part of the roof on our small 5th wheel camper. I have a 3rd panel with the same specs I'd like to install when the weather get's better here in Michigan, but I'm unsure of the best way to install it. The only available real estate for the 3rd panel is at the rear of the camper. I can envision scenario's where the rear will be in shade, but the front is not, and vice versa. I have a 40 amp MPPT controller, and I believe with only 3 panels I HAVE to wire in series, or change them all to parallel, but that would entail replacing existing wiring, and thicker wiring, 8 or 6 gauge rather than the 10 gauge I have now. My thought was maybe I could put in some sort of 3 way switch so that all panels would be connected, or just the front, or just the rear. Does that make sense, and if so, can anyone recommend a switch to accomplish it?
  • BFL13's avatar
    BFL13
    Explorer II
    Feb 12, 2018
    Easier? Put the third panel on with its own PWM controller and just parallel that controller onto the battery bank with the other controller on there now.

    The two arrays will not affect each other, and the two controllers will add their amps, however many amps each that is at the time.

    Do set each controller to the same charging voltage though. (So make that PWM one with adjustable voltage or else set your MPPT one to the PWM's.)

    BTDT
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Feb 12, 2018
    The videos I've seen and reading led me to install my three panels (front mounted) in parallel. Tito's was one of them. Not that much difference series vs. parallel. But I do plan to install one more in the back via 10 gauge to the combiner box. I too felt the back end of my TT would be shaded more than the front. 165 watt panels in parallel should give you plenty of volts for the controller to "shave off" and stuff the batteries.
  • 2oldman's avatar
    2oldman
    Explorer II
    Feb 12, 2018
    GaryS1953 wrote:
    Not sure how they will be if one whole panel is completely shaded.
    You could blanket one of your 2 panels and see how it reacts.
  • GaryS1953's avatar
    GaryS1953
    Explorer II
    Feb 12, 2018
    2oldman wrote:
    Before the switch thing, I'd check the panel specs for bypass diodes. It isn't always a death sentence for series panels.

    I'm a big fan of series and would like to have you stick with that. I'd go the switch route rather than change to parallel.


    All 3 panels are the same specs, with bypass diodes, and the 2 front so far have seemed to be fairly immune to intermittent shading. Not sure how they will be if one whole panel is completely shaded.
  • 2oldman's avatar
    2oldman
    Explorer II
    Feb 12, 2018
    Before the switch thing, I'd check the panel specs for bypass diodes. It isn't always a death sentence for series panels.

    I'm a big fan of series and would like to have you stick with that. I'd go the switch route rather than change to parallel.

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