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ROB12 avatar image

Correct BMV 712 wiring for 4 6v batteries

I have 4 6v lead acid batteries. What would be the correct wiring for the BMV 712? Will I need extra wires then what came with it. Or does neg- connect to one side of the bank and pos+ to the other side? Or connects to one battery. Newbie ?

BMV Battery Monitorbatterywiring
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4 Answers
Rob Howdle avatar image

Hi,

You don't state whether you're connecting your 4 x 6V batteries to give 12V or 24V so i have drawn both. It's very important that you connect ALL negative load cabling to your busbar (or common point) and not directly to the battery negative terminal - otherwise the BMV will be unable to measure the current accurately.

Hope this helps.


Rob


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Its a 12v system .

Thank you

Aviva avatar image

@Ortomaderman The diagram above super helpful - thanks - but I wonder if you could add wiring for the mid-point monitoring / temperature monitoring. Diagrams provided by Victron appear to contradict each other. I have the 12 V system you have identified above, with 2x(2x6V series) both connected to a busbar, and I believe then should next go to shunt and then to load, as shown in your diagram.

Where I am having trouble is with the temp / power supply cable. Where does the "battery ring" end go (positive bus bar?) and then the red/black wires ? The diagram shown by Victron for a similar set up (albeit using 3 banks of 2 x 12V to produce 24V) shows 2 connections to B1 and B2 but not the ring connection... Or are we to separate the wires, and wire ring end straight from 12 V positive busbar to B1 and the separated wire from the midpoint negative to B2?

Finally, their diagram shows all the mid point negs looped together before heading to the shunt. How does one wire that? Gauge etc?

And in that final point... how does the 712 know if one battery is messed up if they are all looped together?

Many thanks!

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Rob Howdle avatar image

Hi,


Sorry - to clarify, i mean the negative of all loads connected (inverter, lights, pumps etc.) need to go to the LOAD side of the shunt. There should only be one connection from the battery negative to the shunt (see attached). Everything will still electrically work if you connect directly to the battery, it just won't be measured by the shunt.


Hope this helps.


Rob


bmv-negative.png (266.1 KiB)
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Maasba avatar image

I just purchased the bmv 712... and the wiring diagram that you show was very helpful. I still have an gap with the "all loads connected here" thing you listed. Let me see if I can clarify with some statement and questions.

  1. I am BRAND new to wiring up inverters etc. But funds are low, so I have to do this myself.
  2. I have a 3000 watt 12 volt inverter charger.
  3. by "All Loads connected here" do you mean that I need to connect the "ground" of the output from inverter.. or do you mean I connect the hot.. of the output of the inverter... I guess I am asking if you can clarify how to connect up "all the loads connected here" when you have a victron inverter.


Thank you for tolerating this dumb question from a total noob, who is not trying to set his rv on fire.

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The NEG of your Multi needs to be connected to the load side of your BMV shunt (the PCB is labeled "Load" or sometimes "Load and Charger" depending on the version of the PCB).

So, to reiterate a few things previously stated:

Your two battery NEGs (one from each 6x2 bank) go to the "battery" side of the shunt. ALL other negative connections go to the other side of the shunt (commonly accomplished by attaching a NEG bus to the load side of the shunt and then connecting everything to the NEG bus). This includes: your Multiplus NEG, all chassis grounds, all load grounds, literally every single ground on the entire system.

If you're using chassis ground for small loads like lights or whatever, just connect your main chassis ground cable to the NEG bus (which is attached to the "load" side of the shunt) and then you can attach your other load grounds to the chassis. The critical thing here is that there is nothing other than the shunt connected to the battery NEG terminals.