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nickdb avatar image
nickdb asked

Shunt midpoint voltage alarms

Hi,


I recently had a shunt installed inline with a bank of 4 victron 220AH gel batteries with probe 2 measuring midpoint voltage.

The setup is a multiplus 2 and mppt, with ESS set to keep batteries charged, all on latest firmware.

Each day a midvoltage alarm is triggered when the variation exceeds 2%, this seems to happen once a day usually around the time the mppt has started producing material power. The alarm clears after a few minutes.


There has been no discharge cycle since the shunt was installed.

Is there any setup/calibration that perhaps should be done?

Is this normal behaviour?

Assistance appreciated.


Multiplus-IIMPPT ControllersBMV Battery Monitor
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nickdb avatar image nickdb ♦♦ commented ·

The alarm triggered again, it coincides with increases in battery charge voltage. In this case there was a sudden drop in temperature (4deg C) because the doors were opened, which resulted in temperature charge compensation raising the charge voltage by almost 0.4V. Once this settled, the alarm reset.

The lower the charge (higher the temp) the smaller the midpoint voltage difference.

Is this an issue with coding logic?

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2 Answers
gigabert avatar image
gigabert answered ·

Hi, sure the connections are in the correct terminals on the shunt? Please check if aux is midpoint. Cheers


Uups too old never mind…

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Trevor Bird avatar image
Trevor Bird answered ·

@nickdb

When the solar charger applies charge current perhaps one battery in one string charges slightly faster than the other battery and causes the slight mid point offset. Over a short duration this evens itself out so the midpoint variation reduces to a negligible amount. If the alarm is a problem, a solution maybe to add a battery balancer to the system so a small amount of current is directed away from the higher voltage battery while it is settling down.

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