#6 wire to panels

Court
Court Registered Users Posts: 5 ✭
in Solar Beginners Corner #1
I have 2 145 watt panels and a Blue Sky 2512iX controller on my boat. The panels are 18 V. Round trip from the batteries (440 Ah) is about 45 feet.

The controller cannot accept more than 28 V, so the panels have to be wired in parallel. To minimize loss, I will use #6 wire (tinned marine cable).

What is the proper way to connect the #6 wire to the MC4 connectors? Is there a MC4 connector that will fit #6 wire? If I can't find an MC4 connector, I will crimp eyes on each cable, bolt them together and pot the connection. The problem with potted connections is that I will have to destroy them every time I have to take the panels down for hurricane warnings.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,011 ✭✭✭✭✭
    #2
    Re: #6 wire to panels

    Might put a combining box at the panels, or since you just have 2 panels use a distribution block to combine them. I think #8 is the largest of the mc4 connectors and most only go to #10.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #3
    Re: #6 wire to panels
    Court wrote: »
    I have 2 145 watt panels and a Blue Sky 2512iX controller on my boat. The panels are 18 V. Round trip from the batteries (440 Ah) is about 45 feet.

    The controller cannot accept more than 28 V, so the panels have to be wired in parallel. To minimize loss, I will use #6 wire (tinned marine cable).

    What is the proper way to connect the #6 wire to the MC4 connectors? Is there a MC4 connector that will fit #6 wire? If I can't find an MC4 connector, I will crimp eyes on each cable, bolt them together and pot the connection. The problem with potted connections is that I will have to destroy them every time I have to take the panels down for hurricane warnings.

    Why is it that you need #6 conductors? That seems like extreme overkill to me. At 30 degrees C, #6 conductors with 90 degree insulation in free air are rated at 105A.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Re: #6 wire to panels

    Court, Welcome to the forum.

    Do NOT cut, pot, or damage the MC4 connectors on your panels. Buy a cable with MC4 connectors on each end and cut it in half. Use the MC4 end to connect to your panels and the cut end to connect to your combiner box.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Court
    Court Registered Users Posts: 5 ✭
    #5
    Re: #6 wire to panels

    I need #6 to minimize the voltage drop. #8 is okay for a 25 Amp electric battery charger, but off grid, I want to be able to use everything I can collect.
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  • Court
    Court Registered Users Posts: 5 ✭
    #6
    Re: #6 wire to panels

    Where can I buy #6 cables with MC4 connectors?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: #6 wire to panels
    ggunn wrote: »
    Why is it that you need #6 conductors? That seems like extreme overkill to me. At 30 degrees C, #6 conductors with 90 degree insulation in free air are rated at 105A.

    Voltage drop problems I'd say; trying to keep the amount under 3%. 23 feet round-trip on a 12 Volt system carrying 16 Amps and you get 6 AWG wire. Those numbers may not be entirely accurate of course. :D
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #8
    Re: #6 wire to panels
    Court wrote: »
    Where can I buy #6 cables with MC4 connectors?
    I doubt that you can. My point was that you don't want to damage the connectors on your panels or you will likely void the warranty. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,654 admin
    #9
    Re: #6 wire to panels

    Usually, the easiest is to purchase a short Male/Female MC4 pre-made cable. Cut in 1/2 and connect the cut ends to your 6 AWG wire runs.

    wind-sun_2204_2851938 Foot MC4 Extender Cable Male/Female

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #10
    Re: #6 wire to panels

    This points out the problem with many of the older technology analog MPPT conrollers, such as the Blue Sky. Nearly all newer design MPPT controllers can take much higher input voltages. They do tend to cost a little more, but as this problem shows, any cost savings can be eaten up with extra wire costs.

    Unfortunately, most people find this out only after they have purchased their charge controller.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,011 ✭✭✭✭✭
    #11
    Re: #6 wire to panels

    There are some wire type branch connectors out there, that have 6" of wire or so coming into a 'Y', where you can combine your 2 panels mc4 connectors, then you'd just have to worry about 2 butt end connections, clip the continuing mc4 connector off the branch and butt in your #6, still no fun in a marine situation.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Hamfast
    Hamfast Solar Expert Posts: 44 ✭
    #12
    Re: #6 wire to panels
    Usually, the easiest is to purchase a short Male/Female MC4 pre-made cable. Cut in 1/2 and connect the cut ends to your 6 AWG wire runs.

    Another question answered...) Thanks, Photo... :)

    Off Grid System; 2175W array; 370ah @ 48v (8 L16 Scrubbers in series); XW MPPT60-150 CC; OutBack VFX3648, FlexNet and Mate

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  • Photowhit
    Photowhit Solar Expert Posts: 6,011 ✭✭✭✭✭
    #13
    Re: #6 wire to panels

    Actually Bill should be creditted with that...

    Attachment not found.

    This is the wire type branch connector I was speaking of, hot linked from outside site, hope that's cool.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Hamfast
    Hamfast Solar Expert Posts: 44 ✭
    #14
    Re: #6 wire to panels

    Ooops..Sorry there, Bill.. :)

    Off Grid System; 2175W array; 370ah @ 48v (8 L16 Scrubbers in series); XW MPPT60-150 CC; OutBack VFX3648, FlexNet and Mate

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  • Court
    Court Registered Users Posts: 5 ✭
    #15
    Re: #6 wire to panels

    The wire Y connector would be perfect, even found them online for $14. Unfortunately, I already ordered branch connectors and a short cable to cut and splice, the $80 solution.

    Thanks for all of the suggestions. I'll be back, because I'll probably want to increase the charging voltage to my Trojan batteries, I think that is an expensive thing to do with a Blue Sky 2512iX. I should have done more research!!!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,654 admin
    #16
    Re: #6 wire to panels

    Our host does sell a version of the Y cables too...

    wind-sun_2203_39000923Multibranch MC4 Connectors, Latching


    Problem is that they (from how I would use them) are limited to parallel connections of a maximum of two parallel strings... Over that, one should use a combiner box of some sort (with fuses/breakers) for proper electrical safety of the solar array.

    Note too--the new forum software stores/serves images locally by default--So those were not "hot linked". However, I do believe in credit, so feel free to place a link to the original site if you wish.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Court
    Court Registered Users Posts: 5 ✭
    #17
    Re: #6 wire to panels

    The local host version of the Y is what I ordered. The wire Y would have eliminated a connector and the need to purchase an extra cable to split.
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