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Diesel_Camper's avatar
Diesel_Camper
Explorer
Jan 31, 2017

Solar Panel Parallel question...

Hi Folks,

A while back I ditched our standard charger converter and have been running g off of a Sunsaver 15 amp mppt driving by a 24V dc power supply (which was ok'd by morningstar). I did this due to the relatively low cost and programmability of the charge controller and the fact that I knew at some point I would be getting solar panels. Well fast forward and I am now getting panels put on and the simplest way would be to wire them in parallel with the 24V power supply. My thoughts are that when 110v is available, I can just run the charge controller as I have been off the power supply and when boondocking the system would run on the solar panels.

My question is can the panels handle being wired in parallel with another power source? I would think they could because I've heard of people wiring multiple panels in parallel and if one were shaded then it would be at a far lower voltage than its neighbor panel...

Thanks for the help!
  • MrWizard's avatar
    MrWizard
    Moderator
    Feb 01, 2017
    diode will stop reverse flow and also lower the solar panel voltage going into the controller

    also it will NOT alleviate the possibility of to much combines amperage being at the input of the 15 amp controller
  • Boon_Docker's avatar
    Boon_Docker
    Explorer III
    Feb 01, 2017
    Put a diode in the line coming from the panels and that will stop current flowing back from the power supply to the panels.
  • SCVJeff's avatar
    SCVJeff
    Explorer
    Feb 01, 2017
    Why not put a DPDT 110vac coil in there ?
    NO Contacts is the shore 24v supply
    NC Contacts are the panels
    Poor mans ATS
    Done..
  • MrWizard's avatar
    MrWizard
    Moderator
    Feb 01, 2017
    Solar voltage well not be exactly 24v
    Example the working voltage of the typical 100w panel is just under 18v
    With an open circuit voltage of 21~22v
    If connected in parallel at night, the panels will be drawing power from your 24v power supply , a parasitic load on your nighttime shore power charging

    This is Not reverse flow from the controller, that does not happen
    This is flow from a power supply into a solid state device ( your solar panels )
    Because the panels are not producing power
    I recommend
    A second controller, with output connect to the batteries

    Also what happens when you have shore power and the sun comes up
    the two together might overload your 15amp controller
  • Diesel_Camper's avatar
    Diesel_Camper
    Explorer
    Feb 01, 2017
    BFL13 wrote:
    I think you mean the panels would be connected to the solar controller in parallel with the 24v power supply being run with 120v input. Not in series.

    I think the solar controller would have difficulties sorting out the correct voltage to apply to the panels. Suggest another chat with Morningstar.

    If you have shore power to run the power supply, why do you need the solar input at all while that is the case? You can have a disconnect switch between the panels and the controller. Off grid just use the solar input.


    Yes I meant parallel. Fixed original post to reflect that. Thanks.
  • 2oldman's avatar
    2oldman
    Explorer II
    Feb 01, 2017
    I don't see a problem with that, although I'd have to give thought to leaving the panels connected when on shore power.. but for now I'm good.
  • BFL13's avatar
    BFL13
    Explorer II
    Jan 31, 2017
    I think you mean the panels would be connected to the solar controller in parallel with the 24v power supply being run with 120v input. Not in series.

    I think the solar controller would have difficulties sorting out the correct voltage to apply to the panels. Suggest another chat with Morningstar.

    If you have shore power to run the power supply, why do you need the solar input at all while that is the case? You can have a disconnect switch between the panels and the controller. Off grid just use the solar input.

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