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imoore avatar image
imoore asked

BVM712 voltage inaccurate

Hello,

I have read through some threads discussing this, but am still not sure the best course of action. I have the BVM712 hooked up. Everything is hooked up correctly and seems to be working well, but the voltage is consistenly lower than the actual measured voltage at the battery. The only connection that could be faulty is the supplied cable with fuse that plugs into the shunt. I have checked it and it is fine. I measure at the point where the cable connects to the battery and get the proper measurement, but the BVM shows less voltage.

I read that one user subbed in a 1A fuse for the supplied 100A fuse and that corrected the problem, but this seems strange that Victron would supply something that gave a faulty reading when the whole point was it's accuracy.


Is this really the best route to try to solve this problem? What are other users doing to correct this?

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4 Answers
Mark avatar image
Mark answered ·

Yes, if you have a 100mA fuse fitted change it for a 1A fuse.

The 100mA fuse has a high resistance that results in a voltage drop across it, which effects the accuracy of the BMV voltage reading.

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imoore avatar image imoore commented ·

Thank you Mark. I have replaced the fuse with the 1A and it has definitely improved the accuracy. The BMV is still showing slightly lower( at this point 12.60 instead of 12.64). Is this considered in "spec"? It just seems strange to me that monitor who's main function would be to give accurate battery readings would be inaccurate and not have some type of function to compensate for this, if so.

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powerstroke2000 avatar image powerstroke2000 commented ·

I'm trying to figure out why Victron wouldn't send out two different fuses, if this is truly the case?

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cpt-pat avatar image cpt-pat commented ·

I had the same issue -- and the same solution, but with a twist:

First, my test instrument: I'm using a Fluke model 117 multimeter that just recently received a factory NIST-traceable calibration. I was reading 3=13.17 volts at the battery terminal, and 13.07 volts on the BVM monitor. A full 0.1 volt error (which matters a lot with LiFePo4 batteries).

I unscrewed the fuse holder expecting to replace it with a 1 amp 3AG type fuse and.. "oh no. They used a mini glass fuse. I don't want to have to stock those on board." So, I temporarily reinstalled the fuse and.. the reading on the BVM hopped up to 13.13 volts - with the same 0.1 amp fuse. "Corrosion! Drat!" Those cheapie fuses Victron used only have to smell saltwater to corrode.

I replaced the fuse with a proper water-tight ATI fuse holder and 1 amp fuse -- and now the voltage reading is correct.

Comeon Victrom: you make a great monitor, so splurge a little on a batter fuse holder!

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offgridsa avatar image
offgridsa answered ·

I have referenced my BVM 712 along side my Fluke 87v and HP Agilent 8.5 count bench meter.

I was pleasantly surprised the BVM 712 was bang on within its full resolution.

As mentioned above I to took readings as close to the where the BVM pcb is reading the voltage and not the battery terminals. Though I did take battery terminal readings for a less critical comparison and there was little difference.

I could have just got lucky with a nice one that fell bang in the middle of tolerance spec range by chance though.

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Chris avatar image
Chris answered ·

Mine measures within 0.03v on my new and certified Fluke 87v.

0.03v is pretty great IMO. I measured at the battery which could account for the small difference. I would like the ability to calibrate the BMV-712 to match exactly.

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powerstroke2000 avatar image
powerstroke2000 answered ·

I'm having a similar issue, albeit, the difference between the Victron 712 and my multimeter (I have two and both so the same result) where my Lithium batteries are showing 13.91V consistently, yet the 712 is showing 13.45V. To me, that is an inconsistent variable, so I'm trying to get to the bottom of this issue. I've been keeping an eye on this daily, and the difference between my meter and the 712 is always there...why is this, and how do I correct it? I do have the Victron set up as the seller of my Battle Born Lithium batteries have suggested.

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