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Is it a bad idea to fit a string of panels with one panel having lower watts?

  • 23-09-2022 9:17pm
    Registered Users Posts: 1,214 ✭✭✭

    My fitter is installating 8x 410w panels in my south facing roof this coming week. I think there is a bit of space for an extra one but perhaps not a 410w, something smaller as a 360w (or likes).

    Would that be a bad idea?

    My fitter was saying that it is possible that system works best having all panels at the same wattage.

    Ay truth in that? Any advice?


  • Registered Users Posts: 9,959 ✭✭✭the_amazing_raisin

    So I think you can do this, but you'll need to design your system to accommodate it

    The panels will be wired in series to make one or more strings and then the parallel strings are combined and connected to a charge controller (which may or may not be part of your inverter)

    The charge controller takes the variable voltage and current from the panel and regulates it down to a steady DC voltage for the inverter and battery

    Most charge controllers now are MPPTs which will try to maximise the power produced from your panels

    I believe for this to work best, all the panels in the string should be of the same type. If one panel is different (for example from shading) then it will drag the rest down

    So to answer your question, you probably can't join the smaller panels to the same strings as the bigger ones. But you could string them to a separate charge controller which will work for those panels only

  • Registered Users Posts: 9,959 ✭✭✭the_amazing_raisin

    Btw, your installer should know about charge controllers and matching different panels already

    If he's not sure then that should start some alarm bells ringing

  • Moderators, Home & Garden Moderators Posts: 4,463 Mod ✭✭✭✭graememk

    Yes it will de rate the rest of the panels to the output of the lowest panel.

    That last panel could be put on a mirco inverter.