BMV712 Setup and configuration

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sharpve asked Feb 4, '22

BMV712 Setup and configuration

I have a five bank 255AH AGM marine battery configuration with four house batteries connected directly to the negative post on the BMV shunt, and one to the main negative buss. The main negative buss is about 25 feet from the four house bank/shunt buss and 20 feet from the fifth battery. The feed from the shunt to the main negative buss is a 4/0 cable and the one to the single battery is a 2.0. I also have a single 410W solar panel running through a VE MPPT 100/50 to control battery charging when no other external charging options are available. Hopefully that explains well enough the basic configuration. I have two questions:

I have 1020AH (255X4) set up in the BMV battery configuration as there are four batteries directly connected to the battery post of the shunt. I presume that is correct or should I set it up for 1275 because the fifth battery is still part of the system and is being charged by the MPPT or other external sources?
Depending on the answer to the above, is it worth it to run another 2/0 cable the last 25 feet or so and take the fifth battery off the main negative buss and connect it to the shunt directly? I dont believe the voltage drop in that short a distance with 2/0 is a big factor but does the BMV need to be set up for the total of all five batteries on the circuit?

Thank you.

DuncanS

BMV Battery Monitor setup

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Answer 1 · 2022-02-05T06:55:50Z

kevgermany answered · Feb 05, 2022 at 06:55 AM

The BMV should be set up for the batteries that charge or discharge through it. From your description, it sounds as if the fifth doesn't do this.

Voltage drop to the fifth battery depends on resistance and current. You'll need to do the calculations. But it sounds as if you're only going to be able to measure the voltage of the bank of four. You'd need to configure and wire the fifth as a starter battery in the shunt/bmv.

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Answer 2 · 2022-02-05T11:17:15Z

sharpve answered · Feb 05, 2022 at 11:17 AM

Thank you for the answer. Is the below configuration what you are referring?

If so, when I check the voltage now between any of the four batteries connected to the shunt as well as the fifth the voltage is the same so I presume I am not going to get much more information other than what I am getting with the display as configured with the four.

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kevgermany ♦♦ commented · Feb 05, 2022 at 01:57 PM

Yes, just like that.

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Answer 3 · 2022-02-05T17:25:29Z

sharpve answered · Feb 05, 2022 at 05:25 PM

My follow on question above was…….when I check the voltage now between any of the four batteries connected to the shunt as well as the fifth the voltage is the same so I presume I am not going to get much more information other than what I am getting with the display as configured with the four.

Please confirm if this is the correct understanding.

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Answer 4 · 2022-02-05T19:52:11Z

kevgermany answered · Feb 05, 2022 at 07:52 PM

In the example diagram the starter/second battery only a voltage measuring wire on the positive terminal. How it is charged/other loads aren't shown. So you may have loads on your single battery causing the voltage to drop which would otherwise be unnoticed. The shunt will see the current through the larger battery only. Note the negative of the single battery is on the load side of the shunt. And no positive load wires to it are shown.

So this gives voltage for single, full info for main bank.

Sorry, I should have said.

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