# question

## What's size mppt blue solar charge controller would I need for a 360 watt solar panel

These are the specs to the solar panel and I want to purchase the correct size charger controller but I'm not sure how to calculate that.

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You did not tell us what Voltage your battery will be.
Let us assume the worst case and you have a 12V battery. I don't mean that in a bad way, just that the lower system Voltages need a larger capacity charge controller.
So a 12V system Voltage would require at least a 30A charge controller in order to get the most energy available from your panel. A 24V system would need a 15A charge controller.

Please have a look at this handy online calculator to see for yourself. Click "MPPT Sizing Calculator" to the right of the blue box.

https://www.victronenergy.com/solar-charge-controllers

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Beaten by WK, but I'll post it anyway (dang phone)..

Hi N. Just divide your panel W by battery V to get a nominal A figure. So 360/12? = 30A. Bear in mind that under charge a 12V batt may spend most of it's time closer to 14V, so then ~25A ensues.

And given your panel will rarely reach 100% efficiency, then even lower may suit better.

Your batt size may help determine your choice. Let's say you have a 100Ah Pb batt, and go by the generally recommended max charge rates of 0.1C to 0.2C, then just multiply by that - so 10A to 20A results. That's just for batt charging, and concurrent loads need adding to that.

So it depends on your needs, and of course your budget. The Victron range is summarized here: https://www.victronenergy.com/upload/documents/Datasheet-BlueSolar-and-SmartSolar-charge-controller-overview-EN.pdf

Anywhere from a 75/15 through to a 100/30 may suit. Do your own sums and post back for confirmation if you will. Sorry for the verbose reply, but just to show you what it's about briefly..

Have fun picking..

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