question

deek avatar image
deek asked

BMV-712 Contactor Compatibility

I would like to use my 712 to operate two existing contactors as low and high voltage cutoffs but I cannot find any info about what contactor would be compatible with the BMS. The contactors I have are 12V I believe 3A max operating current, 200A load current. I have heard there are also currents that get induced when these are activated that can harm the electronics of the sensor (the 712 in this case). My manual doesn't provide any info that I can find about compatible contactors.

Can I hook mine up directly to the BMS 712?

Do I need 48V instead of 12V contactors?

Do I need a separate 12V power supply for the contactors?

If I had 48V contactors, could I hook them up directly tot he BMS? etc.. etc.

Any help or advice would be appreciated!

BMS
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4 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

I think you mean the BMV-712!?

This is in the manual about the relay:


bmv712relay.png (16.8 KiB)
bmv712relay.png (15.1 KiB)
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wkirby avatar image
wkirby answered ·

The relay contacts inside the BMV are rated at 1A up to 30V DC.
These contacts will not switch your contactor directly. You'll need to drive another relay with suitably rated contacts or some other sort of driver suitable for your contactor coil.
The relay contacts in the BMV are potential free, you need to provide the power to drive external circuits.
Any time you drive a relay or contactor coil, you need a flyback diode otherwise the back EMP when the power is disconnected will damage electronics or arc contacts.

The specifications for the relay contacts in the BMV are in the BMV manual on page 39 here:
https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-712-EN-NL-FR-DE-ES-SE.pdf


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deek avatar image
deek answered ·

yes, sorry, thanks for the correction! So, that means my 12 VDC contactors should be compatible with the 712, correct and I shouldn't need to provide a standalone 12V power source for them?

This is probably a dumb question but I only see outputs on the back of the 712 for one relay (one NO, one NC, and one common) but I need to operate two contactors, one for high voltage to disconnect solar to charge controller and lone ow voltage disconnect for the loads. I don't understand how I can do that with only one set of relay output connectors?

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deek avatar image
deek answered ·

sorry, just getting used to this site and didn't notice that I can reply to comments individually. my reply was to matthias before i saw wkirby's post. unfortunately, i am stretching as is and apparently don't know enough to design the arrangement wkirby describes. i have no idea how i would determine what additional relay i would need (or how to wire it in). i do have a standalone 12V power supply that sounds like i would need to use to power the relays and i assume i would use the additional relay wkirby mentions in series with that supply to run the final contactor? i would think though that with a the 712 commonly being used on a nominal 48V bank that i'm not the first noob to try to use 12VDC contactors so i am hoping someone will pipe in with the idiot proof method! also, still confused how two relays can be operated with only one set of outputs.

1 comment
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krystof avatar image krystof commented ·
Hello, I have the same exact question as you do for my system, did you ever resolve this?

thank you

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