question

schuess60 avatar image
schuess60 asked

BMV-712 showing incorrect voltage

I have recently installed 2x Battleborn 100 Ah 12V LiFePO4 batteries in parallel. I also installed a Victron Multiplus Compact 12/2000/80-50 120v along with the BMV-712.

I installed the shunt with the "Battery" to the negative of one of the batteries. The other side of the shunt is connected to the inverter. I have setup the 712 via the bluetooth app exactly per Battleborns recommended settings. I am getting incorrect voltage readout.

Here is a photo of my configuration

Please what am I doing wrong/

BMV Battery Monitor
2 comments
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driftfox avatar image driftfox commented ·

Did you ever find a solution to your problem? I just started having the same problem after my BMV has been working fine for months.

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andrew-marshall avatar image andrew-marshall commented ·
I'm also having the same issue on a new install. I've triple checked the wiring and have measured the voltage between the B1 port and the negative terminal of the battery. It measures exactly the same as the battery voltage.
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4 Answers
Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

@Schuess60 can you get us a closer photo of the shunt itself, specifically the B1/B2 ports?

Offhand my suspicions are that either 1. you have the power supply wire to the shunt PCB plugged into the B2 port instead of the B1 port, or that 2. the fuse in the power supply wire is blown (or half-blown as sometimes happens) or the fuseholder is partially unscrewed, resulting in not getting full vbatt to the PCB.

Double-check your wiring to ensure that you have proper connections and double-check the fuse and fuseholder of the power supply wire and, if no error is evident, give us a few more photos showing more of the installation so that we can better troubleshoot.

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schuess60 avatar image
schuess60 answered ·

The power supply is in B1 and the fuse holder is completely screwed together. The fuses are not blown as the BMV-712 would not get power. I've not heard of a half blown fuse. The vendor, Battleborn batteries believes it may be a bad UTP cable and are sending me a new one. All my wiring has been reverified several times. I have included a picture on this forum.

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Yes, the photo doesn't show us much in terms of the shunt wiring - hopefully BB's new UTP cable will resolve it, though the UTP cable doesn't have anything to do with the voltage at the shunt, only voltage being reported to the display head.

I still recommend that you test for vbatt at the shunt, since a half-blown fuse is indeed something that happens with these glass fuses in particular.

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ebphinn avatar image
ebphinn answered ·

I have this very same problem. It comes and goes. At first the voltage will be accurate. Then it will begin to go down. It might show 11.98 even though the battery is at 100%. Then it will degrade and end up at .01 or .02 It was like this for the last month. All during this time the gage read correct aH and Amps. Now it has gone back up but not to the voltage that me charge controller is showing at the battery. Anyone from Victron have some insight here?

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floridajohnb avatar image floridajohnb commented ·
I’m having the exact same problem.
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driftfox avatar image driftfox commented ·
I just started having the very same issue a couple days ago.
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monterey270ottawa avatar image monterey270ottawa commented ·
Mine just started (about a week ago) reading just under 1/2 the voltage (between 6.0V and 6.3V), on both my house battery and starter battery. Multimeter (and smart battery protect) both report correct ~13.6V. Nothing has changed wiring wise (i've had this setup for two full boating seasons now). I wonder if its a problem with the latest virmware on the BMV? I think there was an update a few weeks back?
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monterey270ottawa avatar image monterey270ottawa monterey270ottawa commented ·
Just checked, im on v4.07 and it says thats the latest version.
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floridajohnb avatar image floridajohnb monterey270ottawa commented ·
My 712 firmware is also 4.07.
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mossy avatar image
mossy answered ·

I got this to 0.03V after firmware update to 4.07. The BMV have the voltage but is not reading it correctly. I would like to re-flash the firmware but don't have the file.

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