BMV 712 Not syncing correctly or recognising full charge

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chris-hayward asked Jul 4, '20

BMV 712 Not syncing correctly or recognising full charge

So I think there is something wrong with my shunt or BMV 712.

I installed it about 4 months ago and it's seemingly worked fine although I have had some trouble getting it up to 100% even though the voltage stays above the threshold (14.4v is what the battery voltage will hold at).

The other day however the BMV read 68% but my batteries had in fact fully drained (low voltage alarm going off on my inverter and lights flickering when I use the pump, etc).
I have no idea wtf went wrong. I fully charged my batteries through solar and the alternator and they reached 14.4v again. I reset the BMV completely and set the settings to:

Charge Voltage 14v
Tail Current 2%
Charged Detection Time 3m
Peukerts exponent 1.05
Charge Efficiency 99%
(All other settings are stock standard)

So I manually synced it to 100% and it showed that the batteries weren't excepting much charge from either the RedArc BCDC1250 or the Renogy MPPT.
Drained the batteries down and now the BMV won't go above 88% despite everything else and the voltage indicating full charged.

I have zero direct negative connections to my battery, everything is wired through the shunt. And the correct orientation. I have the temp sensor on the positive battery terminal.
I have a LiFePo4 Battery bank of x3 170ah wired in parallel.

Please advise or help me! The BMV is reading voltage fine. I think it's confusing amps somehow. It will show amps in and out and they seem correct but its not properly changing the values in SOC or something. It's failing me miserably and I cannot figure it out.

BMV Battery Monitor Lithium Battery

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Trina commented · Jul 30, 2020 at 12:59 AM

What happens when you increase charged voltage to 14.1v?

And tail to 3% (or above 2%)?

2% of (170ah x 3) vs 3% which might be easier to satisfy for a reading of charged (if it is).

And then what are the real readings at your posts after a known full charge?

And when did you last calibrate?

I'd also try less than 99% efficiency for now (and don't VE network your BMV if it is for now -I almost lost my expensive bank due to my MPPT using bad BMV info instead of it's own).

Oh and 2 more things :

Sounds like you had two different issues' one prior to the other (not detecting undercharged state) and now not detecting charged state

One thing that seem to not be standard info but should be perhaps is;

Unplug the UTP cable from BOTH ends and all b1 b2 connections when doing a reset like this. Mine refuaed to reset correctly until I did the UTP cable completely (or replaced) and then calibrated everything correctly. Was a real pain to sort out.

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Answer 1 · 2020-07-04T07:28:56Z

klim8skeptic answered · Jul 04, 2020 at 07:28 AM

Your redarc only has one earth wire (for both batts), how is that hooked up to your battery and shunt?

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chris-hayward commented · Jul 04, 2020 at 08:19 AM

I have the earth/negative going to the shunt.

The RedArc is working fine and the BMV recognises the amps going in.

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Answer 2 · 2020-07-04T13:54:15Z

Daniël Boekel (Victron Energy Staff) answered · Jul 04, 2020 at 01:54 PM

Hi @Chris Hayward

Can you post some pictures of the installation?

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