• Lorraine
    We started with one 80 watt panel and added two 140 watt panels. At that time it was suggested that we parallel wire them with 10 gauge directly to a bus bar in close proximity to the solar controller. It was also suggested to run the 15’ from the solar controller to the batteries with 4 gauge to reduce resistance. The controller is about 8” from the bus bar.

    Then we added another 140 watt panel and parallel wired it into an existing 140 watt panel. Two years ago we added a 195 watt panel and parallel wired it to the bus bar with 10 gauge.

    We assumed everything was working well, but recently someone suggested that mixing panels with different wattages would render the system only operating at the lowest wattage panel.

    Does anyone know if this is accurate information? Or any issues with what we’ve done? If so, suggestions to correct?
  • Ray
    This is a pretty good in-depth explanation with example diagrams https://www.explorist.life/using-mismatched-solar-panel-sizes/

    Basically, when you wire different wattage panels in parallel the lowest voltage panel in the array will draw all the voltages down to its own voltage reducing total watts.
    In a series string its the same but its the lowest amperage panel that will be the most amperage that can pass through so it lowers the total wattage achieved.
    That's why its best to have panels of similar amps and volts. You can sometimes optimize things by wiring stuff in parallel and series arrangments.
    Using an MPPT controller is best for this type of scenario since it can deal with higher overall voltages fed into it. Or a person could use multiple solar controllers splitting the solar arrays into ones that match each other better.

    By the looks of it, you have all 12V type panels in parallel so should be OK, they likely only have minor volt or two differences. They will all be contributing whatever amps they produce.
  • Lorraine
    Thanks Ray. We are going to replace the 80 watt with another 195. Since we only have a 30 amp controller, the one 195 is on a toggle. We’ll leave both the 195s on the toggle for now and then get another 30 amp controller- preferably the same as the one we now have.
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