Series or parallel?

RVoutreach
RVoutreach Registered Users Posts: 7 ✭
in Off Grid Solar & Battery Systems #1
I am considering 2 Kyocera KD180GX-LP 180 watt panels to be run through the new Morningstar 45a MPPT charge controller to charge 2 (maybe 4) Trojan T-105 batteries on my travel trailer. The panels and controller would be purchased from AZ Wind & Sun.

With these specs, would they be wired in series or parallel for my needs? And if you can, explain the "why" of how it should be wired. Thank you.

Max Rated Power (Pmax) 180 Watts
Voltage at Max Power (Vmpp) 23.6
Current at Max Power (Impp) 7.63 Amps
Open Circuit Voltage (Voc) 29.5
Short Circuit Current (Isc) 8.35 Amps
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #2
    Re: Series or parallel?

    Assuming your running a 12 volt system 2x6v T105 or 4 x T-105 in 2 strings then assuming the new Morning Star 45a MPPT has similar specs to the FM60 and XW60 MPPT charge controllers my answer is the choice is yours.

    From the panel specs you give the panel is not a standard rated for 12v systems or big enough to charge a 24volt system in parallel wiring form the specs of which you give are

    Max Rated Power (Pmax) 180 Watts
    Voltage at Max Power (Vmpp) 23.6
    Current at Max Power (Impp) 7.63 Amps
    Open Circuit Voltage (Voc) 29.5
    Short Circuit Current (Isc) 8.35 Amps

    I suspect with a Vmpp of 23.6 volts then the two panels wired in parallel should still allow the MPPT controller to function well. even at equalising max charge rate of around 15 volts

    Wired in series would give a Vmpp of 47.4 volts nearly 4 times your base voltage 3 times equalizing voltage, it depends of where the sweet point of efficiency is on the new Morningstar Controller .
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #3
    Re: Series or parallel?
    RVoutreach wrote: »
    I am considering 2 Kyocera KD180GX-LP 180 watt panels to be run through the new Morningstar 45a MPPT charge controller to charge 2 (maybe 4) Trojan T-105 batteries on my travel trailer. The panels and controller would be purchased from AZ Wind & Sun.

    With these specs, would they be wired in series or parallel for my needs? And if you can, explain the "why" of how it should be wired. Thank you.

    Max Rated Power (Pmax) 180 Watts
    Voltage at Max Power (Vmpp) 23.6
    Current at Max Power (Impp) 7.63 Amps
    Open Circuit Voltage (Voc) 29.5
    Short Circuit Current (Isc) 8.35 Amps


    Either way will work fine, as both schemes create a high enough input voltage to the MPPT.

    One consideration, perhaps especially important on an RV, is that partial shade on any solar panel will reduce the output of that panel an enormous amount...virtually to nothing.

    When wired in series, if even one panel of the string has partial shade, it will significantly reduce the output of the whole string.

    When wired in parallel, when one panel is partially shaded, then the output of only that one panel is reduced, while the other panel continues to output full power.

    For that reason I would wire them in parallel on a small RV system.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #4
    Re: Series or parallel?

    The new Morningstar charge controllers will not be out until around November.
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