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vintona avatar image
vintona asked

MPPT 100W Solar voltage drop

Just a question regarding a 100w Solar panel that I've got connected to a 100/20 Victron smartsolar unit.

Voltage and current from the panel is 20.3, 5.13 on a multimeter.


However, looking on the app: The power output seldom reaches above 75W when charging. And the values settle at 17 ish volts with 4.5 ish amps.

Interestingly, when I initially fold the solar panel out, the controller values go all over the shop for a little while (see video). Voltage starting at 20ish Volts, then dropping.

Just wondered if there was someone more intelligent than I am that can make sense of it all. From my understanding the panel and cable is fine based on the multimeter reading. But I'm not sure why the controller is measuring values that are less than the multimeter - perhaps things change when a load is applied? And why I'm only ever getting 75W, not closer to 100W.

I'd be very grateful for any input!

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MPPT SmartSolar
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1 Answer
Alexandra avatar image
Alexandra answered ·

Voltage under load is different to voltage open circuit. Also for the first bit it will be loading up the panel and dropping it to track where the best power is.

VOC is volts no amps.... So no power.

Also the rating on panels are for when they are 25°C put that sucker in the sun and the voltage drops as it warms up. So yeah.... Solar .... not what it says on the box. Unless you hit the 25°C sweet spot which is my experience is not that often.

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