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crownroyal asked

BMV-702 showing twice the throughput of power/amps coming in/going out

Dear community,

it's been a while since my last post. Hope anyone can help me.
I've recently started a new project converting a RV compartment installation with no-name components + AGM to Victron components + Lifepo4 battery.

The setup:

- 1x Standard Starter Battery (built-in by default) only in scope for the Booster

- 1x Lifepo4 100ah

- Victron Smart Charger 12/30, Victron DCDC Booster 12/30 non-isolated, Victron MPPT 100/30, BMV 702, Victron Inverter Compact 12/2000

- Positive/Negative busbars centralizing connections from/to lifepo4 battery (only)

All the component's negative poles are connected to the negative busbar, which is connected to the BMV 702 Shunt. The output pole of the Shunt is exclusively connected to the lifepo4 battery.

The only negative which does not go through the Shunt is the negative, which is connected to the grounding star of the vehicle/starter battery. This shared negative is used for the Booster.

Now I'm experiencing a strange behavior regarding the correct measurement of the shunt. If I plug in the Smart Charger, which can push up to 30A to the batteries, I see almost the twice the amount of amps on the BMV. Same goes with consumers like the Inverter, expected to be pulling around 200A for running a coffee machine, then I see around 400A. This applies to any consumer of the compartment.

Currently I see two possible causes:

- BMV 702 is faulty (but must be a strange fault) - I rule out an calibration issue. It measuring 0 amps if the main switch is turned off

- Some strange grounding effects. The starter battery and the lifepo4 battery share the grounding mass.

Do you have any idea/experience what could cause this behavior?

Looking forward to your answer. Thank you.

BMV Battery MonitorGroundingamps
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1 Answer
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crownroyal answered ·

Solved. The problem was a misconfigured Shunt voltage of 24mV. Correct value is 50mV.

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Related Resources

Victron BMV battery monitors product page

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