question

artemo avatar image
artemo asked

Bad bmv-700 or did I wire something wrong?

Hello, I am new to this and am having an issue after installing some battleborn lithium batteries in my rv. Hoping someone can help.


  • Replace 4 batteries with 4 battleborn lithium batteries
  • Replace my converter charger with lithium charger
  • Added victron dc-dc charger
  • Added bmv-700 battery monitor

After finishing up, my bmv is showing -77 watt, ~-6 amp draw with nothing on. Changing the battery disconnect relay position doesn’t change much, maybe a few watts. What’s weird is that overnight the bmv shows 0% soc, even though I’m plugged into shore power and the battery voltage remains anywhere between 13.6-14v. It’s my understanding that if the batteries really were drained, that the voltage would be 13.0v or lower. The shunt on the bmv is hooked up correctly, battery side to battery only, and the rest of the grounds on the other side of the shunt.

The rv has a battery control center box (sdc-107a) in which I have removed a transistor as recommended by the manufacturer, to disable its capability of charging the batteries from the alternator. I want only the victron dc-dc to charge the batteries. The battery control center has 3 wire posts. Chassis battery, coach battery, and battery disconnect. The wires connected to these posts are unchanged, with the exception of adding the dc-dc charger the the chassis battery post. I’ll include a picture of the battery control center box and it’s schematic if that would help. At this point I don’t know if wired something incorrectly, or if the bmv-700 is broken because I don’t believe the batteries would be at 13.6v if the soc was really at 0%. Someone please help. Thank you!

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BMV Battery Monitororion dc-dc
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Sounds like the charge current is not going through the shunt or the shunt is connected in reverse.

The only wire connected to the battery negative is a wire to the battery side of the shunt. All other negative (from loads, chargers, chassis) have to be on the other side of the shunt.

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artemo avatar image artemo commented ·

I’ve double checked and the shunt is wired as you said. Only negative wire from the battery is connected to the battery only side of the shunt, the rest of the grounds are on the other side of the shunt.

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kevgermany avatar image kevgermany ♦♦ artemo commented ·
Have you checked the actual current with a clamp meter?
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artemo avatar image artemo kevgermany ♦♦ commented ·
I have not, my multimeter probe wiring broke, will get a new one and report back!
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Paul B avatar image
Paul B answered ·

also check to make sure the small circuit board on the side of the shunt is the correct way around. Just worth a check thats all

also its worth looking at this video

https://www.youtube.com/watch?v=mEN15Z_S4kE


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artemo avatar image artemo commented ·
Will do, thank you
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Paul B avatar image Paul B artemo commented ·

On a side note - you should have a look at the battery installation as its NOT very good - The cabling is NOT to spec in relation to the connections

as to how the batteries are connect to each other - is NOT good - you should be doing it as the below picture to get the best life out of the batteries.

really each battery terminals cable should go to a bus bar (all cables from bateries to the bus bars to be the same length)

all negative terminals to one common Negative bus bar

all Positive terminals to one common Positive bus bar

Then the shunt is connected to the Negative Bus bar on-wards

and the positive LOADS to the positive bus bar.

The below picture I hope gives you the idea of what is best practice

The below means that ALL 4 batteries are equally loaded or charged.

1650701760646.png

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