question

derrainer avatar image
derrainer asked

BMV-712 suddenly displaying a wrong voltage of 0.02V

I had my BMV712 running for some weeks now. This weekend during dischcharge, the main battery low voltage alarm suddenly triggered. The main voltage was displayed as 0.02v.


Link to screenshot: https://photos.app.goo.gl/9BJSLhVN2tJe5Yvk6


this was during normal operation of our camping car. whilst no change was done to anything...
i checked the "real" battery voltage using a DMO and it was 13.x volt.
i quickly inspected all the cabling, but all seemed correct. (and all other values including current from the shunt looked correct..
I then did a reset to factory settings and the voltage was back to normal display (but it started with 100% capacity..) .
It seems to me like a software problem as the only thing i did to resolve it was a factory reset...

Any ideas or suggestions? or is the unit defective?
Regards,
Rainer

BMV Battery Monitorerrorvoltage
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4 Answers
Mark avatar image
Mark answered ·

I would carefully check all terminals and the inline fuse holder to ensure that there is no possibility of a poor connection that could have temporarily gone open circuit.

If anything looks suspect re-wire that joint.

Then if it ever happens again I would check for voltage directory at the B1 positive terminal on the shunt PCB, that way you eliminate all the wiring during your check while the fault is present.

But then again - if the positive supply was to ever go open circuit for more than a few seconds the BMV monitor / display would turn off. So it might actually be the UTP cable between the shunt and the display. So if it ever happens again also give the UTP cable a wiggle at the RJ12 plugs and see if it recovers.

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derrainer avatar image derrainer commented ·

Thanks for the reply,
Yes, i thought the same.. why would it still display 0.02v for over an hour,considering the positive supply for the BMV goes via the same lead??
but still all those suggestions don't really apear to be logical if a foctory reset then resolved the problem?
i checked other things for about an hour, and the bmv still displayed the wrong voltage the whole time. Than after an hour i did a factory reset via the vitron connect app on my smartphone, i was in front off my camper at that time, so no other changes or wiggles on the cable implied... and directly the voltage was reading the correct voltage again. So i don't think it has anything to do with the cabling....


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Mark avatar image Mark ♦♦ derrainer commented ·

I agree with your 1st point/question (that the same positive cable powers the unit) and mentioned this in the last section of my response. I was also unaware how long it maintained the ~0v for.

Historically there have been a few random issues with the UTP cables etc. but I have never heard of the voltage freezing at ~0v and it being rectified with a reset.

Sometimes during first power up is will record a low voltage 'history' of ~0v but this is independent to the main display.

I don't know if there is anything else that I can recommend apart from monitoring it going forward and if it happens again maybe take a short video and speak to your dealer / place of purchase.

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kevgermany avatar image
kevgermany answered ·

The 100% state of charge on startup is a default. You can change this, it then starts on 0% but you'll get low battery alarm. In any case the SOC will resynchronise automatically once the battery is fully charged.

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smoo avatar image
smoo answered ·

I have the same problem. Voltage shows 0.02-0.03. It started a couple of hours after I replaced the starter battery in my van. There was an low voltage alarm. The starter battery was new, it had something around 13V. But I had it disconnected from the rest of the system. I thought, ok, I just have to reconnect. But it didn't help.

Then some hours later (or next day) the BMV also showed 0.02-0.03V for the leisure battery, actually it had 12.7V. This battery has never been disconnected from the BMV.

It still counts the Ah correctly.

Very strange...

I thought testing it with another cable. Can I take a normal telephone cable which as the same connectors, rj11?
But if the voltage data is on the same cable as the power supply it can't be the problem. Because the BMV was always powered.

Later I am going to do a factory reset. Save all data and settings before with a lot of screenshots. Connecting to shore power to fully charge and calibrate.
Not nice. I have better things to do.

Using my van currently for work, driving from building site to building site. Sleeping in there. Heater always on, no sun, I have to watch my battery.

Victron, please help.

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seb71 avatar image seb71 commented ·

First check the connections of the shunt to the batteries and the fuses on those wires. Look for bad contacts, corrosion, broken wire, etc.

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smoo avatar image
smoo answered ·

I found the solution. The data cable was a little bit loose at the back of the computer! Weird that this leads to some false digits instead of showing nothing anymore.

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