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aku avatar image
aku asked

VICTRON BMV 712 RELAY

I just got Victron battery monitor primarily to control have loads in my house (Once battery falls below a certain voltage which is indicative of either no grid or PV energy). So i dont want battery to power AC, Freezer etc.
Now, i have set everything up but not really sure how to physically connect the NO/COM at the back of the monitor to an external Solid State Relay which accepts DC control signal between 3v and 30v.
Pls i need to be told on how to do this. Initially, i connected a wire from COM to the -ve of the relay and NO to the +ve of the relay. It did not work so i believe i am doing something wrong.
Thanks in advance.

BMV Battery Monitor
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2 Answers
Justin Cook avatar image
Justin Cook answered ·

"COM" is the signal that's being passed through, so you can't have a -ve wire to COM and a +ve wire to NO or NC - doing that might have burned up the unit entirely, but you'll have to establish that.

The "relay" on the BMV is just a little switch. The signal wire runs into COM and then out the NO or NC contacts, depending on how you have it set up.

https://www.victronenergy.com/media/pg/BMV-712_Smart/en/installation.html#UUID-6d8692a9-75a0-244f-0e79-82c3eb1f4d0c

https://www.victronenergy.com/media/pg/BMV-712_Smart/en/all-features-and-settings.html#UUID-edcaccf4-fe19-ef15-1942-51d9c9f9c47f

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delf67 avatar image delf67 commented ·
He didn't put voltage into the COM & NO, he connected them directly to the solid state relay terminals.
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delf67 answered ·

The relay is simply a switch that is controlled by the BMV, it is "volt-free".

You need to feed a voltage into the COM terminal of the BMV (between 3 & 30V) then connect the NO contact to the +VE of the SSrelay, then connect the -VE of the SSrelay to the 0V of the battery that supplies the 3-30V to complete the circuit.


Beaten to it again! Must type faster!

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aku avatar image aku commented ·

Perfect. This is what i have cracking my head since. Can't understand why it was not mentioned in the manual

Thanks a bunch. You are a life saver.

A quick one. I guess i can feed the voltage into COM from the battery?

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delf67 avatar image delf67 aku commented ·

You don't say what voltage your battery is, so as long as it's either 12 or 24V, yes that would work (with a suitable fuse of course).

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aku avatar image aku delf67 commented ·

I connected two 12V batteries in series resulting in 24V. When i measure the voltage at the other end, i get 24V which is expected. When i measure at the series connection, i get 12V. I think i would pick the 12V instead of 24V. Also, i would be using a 1A fuse.

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