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What is the rationale of placing the shunt resistor into the negative path of the battery? This creates two different "ground" levels.
Can the BMV-712 be used for high-side current monitoring (i.e. the shunt in series with the positive terminal of the battery)?
The short answer is no, for a few reasons (there may be more).
The BMV takes its negative supply from the shunt, so if you were to mount the shunt on the positive side it would;
- Not see a sufficient voltage, required for it to simply power up/turn on
- Not be able to measure battery voltage (since it would not have the negative 0v reference) and according would not be able to display voltage or power (VxI)
If you just use a SINGLE DC grounding point on the load/charger side of the shunt then you should not have issues with ground loops or even current flow that bypasses the shunt. But you can also ground on the battery side if you are sure that there are no items in the system that have their negative grounded.
Since this goes into a vehicle, "ground" is connected to chassis and must therefore be on the load side of the shunt. And it will be a few mV higher than the battery negative terminal.
This will work, although I'd prefer a high-side current sensor and the battery minus connected to chassis ... Many circuits (e.g. INA219) do this, albeit the simplest solutions do not have sufficient dynamic range.
Thanks for your response - I suspected as much ...
