question

plumbot avatar image
plumbot asked

BMV712 voltage fluctuating

Hi all. Hoping you might be able to help me with an issue with the Victron BMV712. I've added a second battery to the van, and I noticed that the voltage on the Victron app (and the monitor in the van) was fluctuating wildly from around 11V up to 17V. Batteries are connected in parallel and at full charge are 13.5V each.

I hadnt got to the point of changing the battery capacity in the app from 200 to 400amp as yet (as I didnt know at that point that I needed to) so I pulled the batteries out.

Has anyone come across this?

Cheers

BMV Battery Monitor
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1 Answer
Alexandra avatar image
Alexandra answered ·

@Plumbot

Sounds like it could be a loose connection. And is likely if it was disturbed.

Alternatively it is reading a charge that cannot be sunk anywhere. This can happen with lithium.

The possibility of the bms shutting down and switching on again with the voltage overshoot?

Loads of guessing, we would need more information.

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plumbot avatar image plumbot commented ·

Thanks @Alexandra . For a newb, are you able to explain "Alternatively it is reading a charge that cannot be sunk anywhere. This can happen with lithium.

The possibility of the bms shutting down and switching on again with the voltage overshoot?"

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pwfarnell avatar image pwfarnell plumbot commented ·
@Plumbot What is meant is there is a charger on the system but there is no DC load, only battery charging. If the batteries are lithium and when they get full then the BMS shuts off, the current flow stops and the charger takes a little while to reduce current so the voltage increases. Sometime later the voltage reduces and the BMS reconnects. The battery voltage rises and the BMS shuts off restarting the cycle.
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