solar panel wiring RV

Ronvada
Ronvada Registered Users Posts: 5 ✭
in Solar Beginners Corner #1
I have a shell sm110-12p panel already wired to my 5th wheel. being an older panel it has two boxs under it I think one is plus and one is minus.
I just bought another 110watt panel with mc4 connectors. I think I know how to wire it but I would like some suggestions. Might help.I have purchased a 6FT extenion with mc4 connectors on one end.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #2
    Re: solar panel wiring RV

    Generally, the answer is to just connect the two panels in parallel (+ to +, and - to minus)--just like if you wanted to parallel two 12 volt batteries for your RV.

    Depending on the charge controller you have--there are more expensive MPPT type charge controllers (maximum power point tracking). With these type, many times you have the option of placing two (or more) panels in series--allows you to use smaller wire gauge for Array to Charge Controller run.

    However, I would guess you have the less expensive PWM (Pulse Width Modulation) for your setup--and parallel connection is the only one that will work (assuming Vmp~17.5 volts or so).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Ronvada
    Ronvada Registered Users Posts: 5 ✭
    #3
    Re: solar panel wiring RV

    Thank you I have a generator back-up .I have A 30 AMP controler just needed more suggestinos on who to wire the boxs they are marked plus and minus.
    Both panels are 17.? volts and 6.? amps
    Just didn't want to mess things up.
    Thank You
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #4
    Re: solar panel wiring RV

    If you have more than two panels (or series strings of panels in parallel), you should put a series fuse/breaker in each + parallel connection (or use a combiner box with fuses/breakers). This prevents three "good panels" from back feeding a shorted panel.

    The fuses are typically rated about 2x Isc (rounded down/up to nearest standard size). Many panels have the series fuse rating listed in their data sheet.

    Goes into the "not needed to work" but a "good idea" to reduce the chance of fire.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • soleil
    soleil Solar Expert Posts: 45 ✭
    #5
    Re: solar panel wiring RV

    I used two of these "Y" connectors -- one male and one female -- to connect my two solar panels in parallel: http://www.solar-electric.com/mumc4colam.html. You just plug the "+" from each panel into one of them and the "-" from each panel into the other.
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #6
    Re: solar panel wiring RV

    If you need a pair of those per panel, then that almost offsets the price difference from a junction box PV.
    soleil wrote: »
    I used two of these "Y" connectors -- one male and one female -- to connect my two solar panels in parallel: http://www.solar-electric.com/mumc4colam.html. You just plug the "+" from each panel into one of them and the "-" from each panel into the other.
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  • soleil
    soleil Solar Expert Posts: 45 ✭
    #7
    Re: solar panel wiring RV

    They can be had for about half that elsewhere. I just like to show things at the forum sponsor when possible. I don't know why NAWS has them for so much. NAWS usually has very competitive pricing. ;)
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  • Ronvada
    Ronvada Registered Users Posts: 5 ✭
    #8
    Re: solar panel wiring RV

    What are you talking about?????????????????
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: solar panel wiring RV

    They're talking about using 'Y' connectors which have two of one type MC4 connector and one of the other so that panels with MC4 connectors can simply be plugged in to parallel wiring. That and the fact some panels (like Kyocera 135's) are also available with the old junction box standard: no MC4 connector.

    You are adding one panel which has MC4 connectors to one panel which does not have MC4 connectors. All you need is an MC4 "extension" cable; one end will plug in to each end on the new panel, cut the wire in half and you have "pigtails" for wiring in to the existing box.

    To determine which is (+) and which (-), use a DVM. Put the probes on one way: if it reads +V then the red lead is on (+) and the black on (-). If it reads -V it's the other way 'round.

    Does that help?
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  • Ronvada
    Ronvada Registered Users Posts: 5 ✭
    #10
    Re: solar panel wiring RV
    Cariboocoot wrote: »
    They're talking about using 'Y' connectors which have two of one type MC4 connector and one of the other so that panels with MC4 connectors can simply be plugged in to parallel wiring. That and the fact some panels (like Kyocera 135's) are also available with the old junction box standard: no MC4 connector.

    You are adding one panel which has MC4 connectors to one panel which does not have MC4 connectors. All you need is an MC4 "extension" cable; one end will plug in to each end on the new panel, cut the wire in half and you have "pigtails" for wiring in to the existing box.

    To determine which is (+) and which (-), use a DVM. Put the probes on one way: if it reads +V then the red lead is on (+) and the black on (-). If it reads -V it's the other way 'round.

    Does that help?
    Yes, thank you. I have ordered a 6 ft extension
    cable with MC4 connectors on one end to hook in to the boxs on each end. They are marked minus and plus.I was hoping my panel had branch connectors but no such luck.Thank you I needed a postive responce.
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