question

rakiv avatar image
rakiv asked

Mixing different size solar panels

I’d like to add a second smaller solar panel in parallel to my current setup that is a Renogy 175-watt panel (VOC 21.6, ISC 10.35, VMP 17.95, IMP 9.75), a SmartSolar MPPT 75/15, and 12-volt battery pack. I’d like to add a Renogy 100-watt panel in parallel (VOC 22.3, ISC 5.86, VMP 18.6, IMP 5.38). Can the SmartSolar MPPT work efficiently with this combination of panels? If so, would there not be a huge loss of combined watts since the VMP values are so close, and that the MPPT would use the lower value of 17.95? Lastly, would I need to upgrade to a MPPT 100/20 since the combined IMP (9.75+5.38) is slightly greater than 15? Thank you.

MPPT SmartSolar
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pwfarnell answered ·

I can not give you a definitive answer on the combined panels, but i agree that as they are close in voltage they should work reasonably well.

The number 15 does not refer to the maximum panel amps, but the maximum battery amps. If you are charging at about 14Volt, the 15 Amp limit gives you 210W so you will not obtain the combined power output in peak sun conditions but during poor light you will get more than with the single panel. If you are after peak output in full sun then you will need a 20Amp controller.

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