question

garyartista avatar image
garyartista asked

BMV shows wrong voltage

I just changed my batteries from wet cell to AGM. It was charged for several hours and showed 100% charge. We ran the boat for an hour afterwards and the BMV showed that the batteries were receiving a charge. We sat in the sun, getting some amperage. We used the batteries for some low useage activitie, such as a small fan and of course the refrigerator. Then we ran the boat for another hour. At the end of that period the BMV showed we had used 50 amp hours, with a SOC of 92%. At that point I realized that I had not changed the battery capacity. I changed it to match the batteries. The next morning I checked the voltage using two different volt meters. They showed 25.96v while the BMV showed 24.41. I never had that happen with the previous batteries.

There are two AGM 161 ah batteries and two starter batteries. There is a Victron 24v inverter, just a year old. There is a Victron Solar MPPT 75/ 15regulator that has been working well. , The BMV is about 2 months old.


I can not find anything stating that there is a different setting for AGM batteries. Mine are made by Genois, a Polish manufacturer.


Why does BMV show the wrong voltage and how do I correct it?


thanks

BMV Battery Monitorbattery system voltage
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5 Answers
garyartista avatar image
garyartista answered ·

I read that you should check the voltage at the shunt. I did so and it matches the output. So for some reason at the main 24v circuit breaker I show 27v. Any thoughts?

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garyartista avatar image
garyartista answered ·

Further info. One of the negative batt cables was loose. It came off as I was tightening it. Of course the power to the BVM was cut. When I got the cable tight, the BMV still reads 24.4 or so, but the battery shows 99% full vs 80%. I am not sure what to believe with regards to the BMVB at this point with regards to SOC. Any suggests as to what I should do?


thanks

1 comment
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pwfarnell avatar image pwfarnell commented ·
One of the settings in the BMV is start at 100%. In other words, whenever power is lost and then reconnected, the BMV will automatically go back to 100%. I expect that you have this option set to yes and this is what happened. Hence the reply to wait, once the batteries have been through a charge cycle to full everything will be OK.
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bruces avatar image
bruces answered ·

Go grab a beer & relax!

Press the up & down buttons at the same time. (reset)

Allow everything to just happen for 24 hours while drinking more beer.

Come back & report.

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garyartista avatar image
garyartista answered ·

The beer worked. I had to experiment with beer brands, however, as you utterly failed to state which to use. I tried wine, too, and it worked as well, which you also failed to state. :)

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klim8skeptic avatar image klim8skeptic ♦ commented ·

Grab some popcorn instead, and watch Victron's BMV movie..

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Alistair Warburton avatar image
Alistair Warburton answered ·

Make sure you have apropriate bulk, absorbe and float voltages, for your speciffic cells, AGM's are very sensitive to dammage due to gassing as they cant be replenished if the meager amount of electrolite is boiled off.

most AGM's have recombiners, to prevent electrolite loss but if you push them too hard, by not having temperature compensation in place or simply using inapropriate settings you will dammage them quickly.

I use lithium so cant tell you how this is set up but it will be in there somwhere.

I will keep the beer fix in mind, I like that kind of fix :-)

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