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iceblitz avatar image
iceblitz asked

Can I use a 400W solar panel on the 75/15 SmartSolar controller?

I have a 75/15 SmartSolar MPPT controller, and a 120W panel. This is not sufficient, and I want to maximise the charging power on mornings and evenings.

So I was wondering if I could install a 400W solar panel on the MPPT despite the controllers max wattage rating of 220W?

IF I can do this, where the heck does the excess power go? Surely it can't be dissipated as heat, because there is not enough cooling on the MPPT to remove 180W of waste heat. I hope someone can explain this to a dummy like me :D


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MPPT ControllersMPPT SmartSolarsolar sizing
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dansonamission avatar image
dansonamission answered ·

There is no excess power, the MPPT will pull power from the panel as required, panels don't push power out.

The 75/15 means, a maximum PV voltage of 75 and max amps output at battery voltage of 15. As long as your PV voltage is less than the maximum of 75v for this MPPT you'll be ok.

https://www.victronenergy.com/mppt-calculator

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iceblitz avatar image iceblitz commented ·
Thank you for your answer. But what do you mean the solar panel dont "push power out". To me it seems like it absolutely does.


If I connect a solar panel directly to a battery, it will charge it, as there is both current and voltage coming out of the panels terminals.


That means that the controller has to cut or reduce power somehow, to my understanding. If the controller can cut or reduce power without getting hot, it has to apply resistance (ohms law). How is it doing this?

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