HELP! MC4 and Junction Boxes

lwilli01
lwilli01 Registered Users Posts: 12 ✭
in Solar Beginners Corner #1
Okay, I have two small panels that I've hard wired together - I had another hard wire set-up into the charge controller. What I wanted to do was set up a "quick disconnect" between the panels and the charge controller.

So, I bought a MC4 cable, cut in half and then realized, Oh crap! This is one wire and I need a positive and a negative.

What do I do?:confused:

Thanks in advance for your help!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: HELP! MC4 and Junction Boxes

    I think we may need a little clarification on the matter.

    You have how many panels that you're trying to connect in parallel to the charge controller?

    How many of these have MC4 type connectors?

    You're trying to arrange for a disconnect between all panels and controller or just the latest addition?

    Note that MC4 extension cables have a (+) connector at one end and a (-) at the other. Typically one gets cut in half, the MC4 connectors attach to the (+) and (-) of the panel(s) and the "wire ends" get spliced to the charge controller.

    MC4's aren't the easiest "quick disconnect" either, nor is it safe to break their connection while the panel is putting out current.
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  • lwilli01
    lwilli01 Registered Users Posts: 12 ✭
    #3
    Re: HELP! MC4 and Junction Boxes

    I have two solar panels in parallel, again without the MC4 connectors - they're hard wired.

    Then I had an additional wire from the last panel, hard wired into the charge controller.

    I bought the MC4 hoping to cut it in half so I can use the plugs as a means to connect and disconnect the solar panels and charge controller.
    Hoping I could use the opposite ends to hard wire to the panel and charge controller.

    Am I making any sense?

    If this was wrong thinking on my part please tell me! :roll:
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  • lwilli01
    lwilli01 Registered Users Posts: 12 ✭
    #4
    Re: HELP! MC4 and Junction Boxes

    Oh, and the MC4 I have - is just one wire. There are not two like the ones I used on my panels with a positive and negative wire.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: HELP! MC4 and Junction Boxes

    Well the MC4 extension cable should be (+) at one end and (-) at the other. Therefor cutting one in half would leave you with a MC4 connection in the middle and two wire ends. That should do it. Technically you only have to disconnect one side to break a circuit (i.e. standard wiring practice of switching off the positive).
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  • lwilli01
    lwilli01 Registered Users Posts: 12 ✭
    #6
    Re: HELP! MC4 and Junction Boxes

    So the two wire ends (sorry I'm so inexperienced in this stuff but I'm learning)
    Can I just divide them to attach to the positive and negative terminals?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: HELP! MC4 and Junction Boxes

    You have the wire; does one end plug in to the other? If so, there you go.

    Keep in mind MC4's latch when plugged tgether, and you will probably need one of these to get them apart:
    http://www.solar-electric.com/ditoformc4co.html
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