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solargeek asked

How does an Overkillsolar BMS work with a SmartSolar MPPT 150/35?

I'm building an off-grid ESS for my cabin and I have a 280 AH 24V LiFePO4 battery with an Overkillsolar 24V 100 Amp BMS. I'm using a SmartSolar MPPT 150/35 charge controller. So my question is this: Who is in charge of charging? The BMS is an impressively capable device with a lot of intelligence and will manage the batteries just fine on its own. Do I set the SmartSolar charge voltage limits high and let the BMS regulate current, or the opposite? Or something else? Is the SmartSolar OK with a BMS regulating current? The two devices cannot communicate. Any help here would be appreciated.

MPPT SmartSolarBMS
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2 Answers
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nebulight answered ·

Moved to Modification Space for more visibility. Check out Louis' thread here: https://community.victronenergy.com/questions/76159/victron-venusos-driver-for-serial-connected-bms-av.html

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Louis van der Walt answered ·

You can add a rPi with the VenusOS or a full GX device and the bms and the MPPT will be working together.

If you want to only have the MPPT and the BMS then you will have to set the MPPT's battery voltage to what you want the battery to be charged to (I suggest 3.45V per cell). The MPPT will try to get to that voltage and the BMS will balance where needed and protect if one cell go over the full voltage. Then this happens the BMS will disconnect and the MPPT will there is no battery until it release. Not the best way, but it will work.

If your cells are nicely balanced then the BMS should not have to protect and as the MPPT will push to reach the battery voltage it will scale down PV production when it does reach that voltage. You might need to lower the battery voltage if you see(or hear) it protects to often. You might loose a 1-2% SOC that you cannot use, but that is small to the rest of the capacity you can use.

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