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karl-erik-rabakukk avatar image
karl-erik-rabakukk asked

Switching Multiplus on/off with external relay/switch ("remote" port), overriding Multi Control

Hello,

I have a Multiplus 12/1600/70 with a Digital Multi Control GX panel. I have a BMV-712 monitor and plan to set its relay to shut off DC loads in case of low SoC. With the same relay signal, I need to stop the Multiplus from drawing current from battery (in case of not being there to turn off manually).

Main question: Is such switching possible through the "remote" port, or will the Multi Control override the remote signal?

If is possible, as this post https://community.victronenergy.com/questions/60743/digital-multi-control-gx-w-remote-onoff.html suggests, is it also possible to program the remote port so only current drawing is off, but charger can still function?

If is not possible, would it be smartest to A) shut inverter DC feed off via external relay (then still also no charging from multiplus as long as battery is low, and thats a big relay), B) shut AC loads off via external relay (then still inverters zero load current is draining battery) or C) program Multiplus somehow to detect low SoC itself and turn itself off (I have a 560Ah DIY LiFePo4 bank, so this is maybe not the most accurate, and then still same question, can it shut down only the load side, so charging is still possible?)

All the best

MultiPlus Quattro Inverter Charger
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5 Answers
wkirby avatar image
wkirby answered ·

What type of battery are you using? If lithium and you are not using the temperature sense input, then you could use the temperature sense input with the two signal BMS assistant to present a "cell low" condition which would disable inverting but charging would be allowed.
I think this is the most elegant solution.

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karl-erik-rabakukk avatar image
karl-erik-rabakukk answered ·

Seems clever, but I don't understand, what exactly to connect to the temp sense ports?

I have a DIY raw cell + Daly BMS LiFePO4 battery.

Altough as I understand, the temperature sensor is not necessary when using lithium battery, it will maybe still be in use because of this: https://community.victronenergy.com/questions/142809/multiplus-alarm-relay-programming-by-temperature-i.html

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bazil answered ·
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karl-erik-rabakukk avatar image
karl-erik-rabakukk answered ·

@bazil

I ended up switching Daly BMS to Overkill programmable BMS and set all needed protections for battery there. In addition I bought the MK3-USB interface and set Multiplus to turn off below a low voltage treshold. This way with voltage limit it also turns inverter off already at 25...30% soc with high power applications (electric water boiler), while letting battery drain to ca 10% soc with lower power loads (charging laptop).

I didn't try connecting BMV to Multiplus.

Using remote port simultaneously with MultiControl panel, I remember the remote port overriding the panel, but not sure anymore. Didn't use in end.

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bazil avatar image
bazil answered ·

@Karl Erik Rabakukk

Thank you so much for your feedback; it appears the suggested solution (temperature sensor on Muliplus connected to BMV relay) is indeed working. I had to set the mini relay off time to an hour on the BMV.

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