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marksman-ro avatar image
marksman-ro asked

MPPT + BMV-712 relay to switch charger on/off

Hi,

I have a 100Ah gel battery and a 3rd party inverter+charger. The system acts as a UPS, charging the battery when the mains is on and delivering power from the inverter when mains is off.

I want to add about 400 Wp worth of PV panels, 2 series + 2 parallel, connected to a Victron MPPT 100/30 so I can use solar power when available and use the BMV to switch the charger on when batteries are low (typically at night).

I've been studying the available docs and I can't figure out whether I can connect the BMV to the MPPT via the Ve.Direct port. I know I can do that via a GX device but I want to use the Bluetooth on the BMV for monitoring and leave the GX out.

Another thing I don't understand is that if both the charger AND the MPPT are outputting to the battery is there any risk to blow off the MPPT or the charger.


MPPT ControllersBMV Battery Monitor
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kevgermany avatar image
kevgermany answered ·

Firstly if you download/install Victron connect, go into the demo library you can see the options for switching the relay in the BMV. Check the specs, it's relay is low power.

You are probably at more risk of blowing your battery than anything else. Normal charge rate on a 100Ah battery would be about 10A. MPPT and charger should co-exist ok as long as your charger is a decent one.

Why do you want to connect BMV and MPPT?If you want Bluetooth monitoring, the Bluetooth MPPTs work well.

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marksman-ro avatar image marksman-ro commented ·

I want the BMV because I need the relay to switch the charger on/off.

The entire system logic is:

- if solar power is available, inform BMV to switch charger off and then use MPPT to top off the battery

- if no solar power, let BMV to switch charger on

- if there is excess solar power, charge a backup battery or turn off charging while telling the BMV to switch the charger off.

The inverter/charger is a generic one, I've had it for over four years and used it with an automotive battery which had less capacity than my needs.





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