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Preferred method to connect MC4 to 4AWG bare cable

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  • Preferred method to connect MC4 to 4AWG bare cable

    I have searched for an answer on the web to no avail. Perhaps I am using incorrect phrasing.

    I have a 6 panel (600W) Renogy system wired as 24V to feed a Renogy 60A CC.
    The panel leads are tied to MC4 branch connectors - terminating to 1 each M & F.
    The only way I see to connect the 4AWG cables from the CC to the panels is by attaching short 8AWG MC4 pigtails at the panel bank to one side of ANL fuse holders and the 4AWGs out to the CC. I can't find a 4AWG MC4...
    Am I doing this right please?

  • #2
    I think the preterred method is to go through a combiner box that has breakers. The breakers need to protect to #10 Wire from the panels to where you are paralleling them to increase the Amps. At least that is what I assume you are doing, If you are not exceeding 30 Amps 10 Ga wire should work and you can find MC-4 pigtails in that size.
    9 kW solar. Driving EVs since 2012

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    • #3
      Originally posted by Soulearner View Post
      I have searched for an answer on the web to no avail. Perhaps I am using incorrect phrasing.

      I have a 6 panel (600W) Renogy system wired as 24V to feed a Renogy 60A CC.
      The panel leads are tied to MC4 branch connectors - terminating to 1 each M & F.
      The only way I see to connect the 4AWG cables from the CC to the panels is by attaching short 8AWG MC4 pigtails at the panel bank to one side of ANL fuse holders and the 4AWGs out to the CC. I can't find a 4AWG MC4...
      Am I doing this right please?
      No.. Do what Ampster said. You run the panels to a box with breakers that protects each 10ga wire.. when the power leaves the breakers, you run into a distribution block (or bus bar), and then run the 4ga wire back.

      There's no such thing as a 4ga MC4 connector.. I believe the MC4 connectors themselves are only capable of 30 amps so it doesn't make sense for them to make one for a larger cable.

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      • #4
        Well that's fine then. Thanks for your wonderful assistance gents. I will get the proper equipment then.

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        • #5
          Originally posted by Soulearner View Post
          Well that's fine then. Thanks for your wonderful assistance gents. I will get the proper equipment then.
          Have you calculated what wire size you need for how those panels are connected?
          Are they all connected in parallel? If the voltage is 24 volts and you have 600 Watts that calculates to 25 Amps. Unless you are going a long distance you may not need 4awg wire from the combiner box. Is my assumption correct about these being in parallel and at 24 volts.
          9 kW solar. Driving EVs since 2012

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          • #6
            Originally posted by Ampster View Post
            Have you calculated what wire size you need for how those panels are connected?
            Are they all connected in parallel? If the voltage is 24 volts and you have 600 Watts that calculates to 25 Amps. Unless you are going a long distance you may not need 4awg wire from the combiner box. Is my assumption correct about these being in parallel and at 24 volts.
            The six panels will be wired in three sets of two for 3x24V, to three breakers, to a combiner (or distribution) box, to ~50' of 4AWG cables to the dwelling. Several charts show the loss at <3% for this size and length.
            Finding the correct breakers is proving difficult due to my lack of familiarity; Each panel is 6.4A short circuit = 12.8A Isc in series of two. OK, so I guess 3 20A breakers are needed. But the voltage needed screws me up since the Voc is 21.5 each (43Voc in series) so I guess a 24V breaker is inadequate. "Sigh......."
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            • #7
              The breakers are rated by Amperage but they should also be picked to carry at least the voltage. Their purpose is to protect the wire so on the #10 you could use up to 20-30 Amp breakers. If the Amperage to the controller doesn't exceed 30 Amps you could use a 30 Amp breaker because #4 can carry up to 60 Amps but your system will never see that. I assume you know the math since I still don't follow the details but am basing all this on 600 Watts at 24 volts.
              9 kW solar. Driving EVs since 2012

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              • #9
                Still putting in my system, but a higher voltage and location of where this is combined then sent into the MPPT charge controller did wonders to bring the wire size down.

                I had something similar when I was trying to figure my 600 watts of panels, and changing panel voltage from 12 VDC to 36 VDC worked for me. I changed it from 6 panels in parallel to 3 in series 2 in parallel, and that allowed me to get 24 feet of wire from the combiner to the charge controller. One of my limitations was the charge controller only accepted 6 gauge wire, so that was my max thickness.

                After I decided on that, someone pointed out I could move the combiner even closer by moving it from the roof to inside the battery compartment and that will cut down on the wire size needed.

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                • #10
                  Originally posted by chrisski View Post
                  ........

                  After I decided on that, someone pointed out I could move the combiner even closer by moving it from the roof to inside the battery compartment and that will cut down on the wire size needed.
                  And in the future it make testing an diagnosis much simpler than having to climb onto the roof.
                  Last edited by Ampster; 08-16-2020, 12:00 AM.
                  9 kW solar. Driving EVs since 2012

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