BMV-712 installation- 24v system

[pda1]

I'm trying to figure out how to correctly wire up a Victron BMV-712 (Smart) to my system.
Batteries are- 2- 12v 100ah Battle Born in series= 24v

The Victron instructions are clear, somewhat, but don't include a 24v installation procedure.

Any ideas?

Thanks

 

[HighTechLab]

The 24v installation procedure is the exact same as the 12v procedure. Just connect the little red positive wire to your pack's positive terminal, and the shunt is placed per the diagrams in the manual.

 

[rmaddy]

I have 2 12V batteries in series and a BMV-712. Image battery A (BattA) on the left and battery B (BattB) on the right. The would be a series connecting cable between the two batteries. Let's say it's connected to the BattA+ terminal and the BattB- terminal.

With that setup you would connect the battery end of the shunt to the BattA- terminal. The supplied red wire would go into the B1 connector of the shunt and run to the BattB+ terminal.

Since you have batteries in series it might be nice to setup the BMV-712 for midpoint monitoring. If you wish to do this use the other red wire from the B2 shunt connector to the BattA+ terminal. Or you might want to get a temperature sensor and use that with shunt connector B2. The choice is yours.

A lot of this is shown in diagrams in the Quick Installation guide you can find on Victron's website.

 

[pda1]

I have 2 12V batteries in series and a BMV-712. Image battery A (BattA) on the left and battery B (BattB) on the right. The would be a series connecting cable between the two batteries. Let's say it's connected to the BattA+ terminal and the BattB- terminal.

With that setup you would connect the battery end of the shunt to the BattA- terminal. The supplied red wire would go into the B1 connector of the shunt and run to the BattB+ terminal.

Since you have batteries in series it might be nice to setup the BMV-712 for midpoint monitoring. If you wish to do this use the other red wire from the B2 shunt connector to the BattA+ terminal. Or you might want to get a temperature sensor and use that with shunt connector B2. The choice is yours.

A lot of this is shown in diagrams in the Quick Installation guide you can find on Victron's website.

I have all of the documentation. Too confusing. Saw midpoint monitoring setup but still have no idea why to use it.

 

[rmaddy]

Saw midpoint monitoring setup but still have no idea why to use it.

To make sure your two batteries are staying at the same voltage. That's important with the batteries in series. Also make sure you get the two batteries to the exact same SOC before hooking them up in series. I would think Battle Born has instructions on doing that.

 

[sunshine_eggo]

Midpoint monitoring isn't a bad thing as it shows if the 12V are out of balance with each other. If one is at 11V and the other is at 13V, bad things happen.

You have to choose between using a temp sensor or mid-point monitoring.

 

[pda1]

Midpoint monitoring isn't a bad thing as it shows if the 12V are out of balance with each other. If one is at 11V and the other is at 13V, bad things happen.

You have to choose between using a temp sensor or mid-point monitoring.

Hmmm, sounds like mid-point monitoring would be a better idea.

Not sure if this applies but Battle Born says to make sure your batteries are the same voltage before connecting them to the PV solar system. This can be accomplished simply using the Victron IP65 (my battery charger) to bring each battery, one at a time, up to correct voltage.

 

[rmaddy]

I would take it further. After you charge each battery, connect the batteries in parallel and connect the charger. Put the positive lead on one battery and the negative on the other. Fully charge the batteries and let them sit together, in parallel, overnight. Then they will be at the same SOC and fully ready to be put in series.

 

[sunshine_eggo]

I would take it further. After you charge each battery, connect the batteries in parallel and connect the charger. Put the positive lead on one battery and the negative on the other. Fully charge the batteries and let them sit together, in parallel, overnight. Then they will be at the same SOC and fully ready to be put in series.

+1. Technically, this is almost overkill, but it is NOT a bad idea if you have the time to do it.

If you read the BB manuals, they actually recommend 12V used in series to be charged to full individually once a year to maintain balance. Given that BB is arguably the highest quality batteries available, I would apply any maintenance recommendations to a lesser battery.

 

[pda1]

+1. Technically, this is almost overkill, but it is NOT a bad idea if you have the time to do it.

If you read the BB manuals, they actually recommend 12V used in series to be charged to full individually once a year to maintain balance. Given that BB is arguably the highest quality batteries available, I would apply any maintenance recommendations to a lesser battery.

I'll go with BB's recommendation. They recommend charging once per month for batteries in series;

How to Maintain the Batteries (this is just for the 12v 100ah BB)

How to Maintain the Batteries
Battle Born Batteries require very little maintenance. If your batteries are in series and not being
charged by a multi-bank charger it is recommended that you fully charge the batteries individually once
a month if the system is used frequently. This will internally balance your batteries to ensure that they
will reach their expected life span and allow you to get the full power out of them with each use. If your
batteries are in parallel this is not necessary, just make sure the batteries are charged to 14.2V – 14.6V
frequently for internal balance. Our BMS has a built-in passive balancing system that will take care of
this for you.

 

[sunshine_eggo]

Once a month? Man. I misread that!

 

[HRTKD]

Once a month? Man. I misread that!

Screw that! I have better things to do.

My recommendation: If you need a 24v battery, build a 24v battery.

 

[rmaddy]

BB does sell a 24V battery. Much better choice than two 12V in series.

 

[pda1]

Once a month? Man. I misread that!

It's not so bad. Certainly it doesn't take long to charge 'em up.

 

[sunshine_eggo]

There are 12V active balancers that work to keep 12V batteries that are in series at 12V. Concept is identical to active cell balancers within an LFP battery.