Help me understand SmartSolar MPPT 75/15 specs/maximums?

DIY
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Hi all- I want to charge my 100Ah 12.8V LiFePO4 battery from my SmartSolar 75/15. I have two 195W panels, and I’m trying to understand the maximums in the specs for the Victron unit.

In the specs, it says 15A max, but at “12V” the maximum wattage is 220W, and at 24V it’s 440W. I thought earlier that it meant for 12V (nominal) panels the max was 220W, but after trying it, I think that means for charging 12V batteries, right? So I’m limited to 220W.

So to better utilize my 390W of panels, I’ll need to upgrade my controller, right? Can I use two 75/15 units if I want?

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A 75/15 can output max 15A.
15A at a 12V battery is around 220W (at 14,6V charging voltage).
15A at a 24V battery is around 440W (at 29V charging voltage).

75V is the maximum for the PV voltage.

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ah, OK. I missed that. 15 amps OUTPUT. Thank you.

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Yes, you can use 2 75/15 controllers. You can connect them together on a VE Smart Network via Bluetooth and get them to synchronise charging to maximise performance..

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As an experiment, I put my two batteries in series and changed the controller over to 24v. I’m now able to get ~400W. Thanks for the explanation.

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