How to find current from battery side ( not motor current ) foc sdk bldc 3 shunt resistor

Hello dear STM community family,

I have been trying to develop bldc motor controller for some weeks

In motor control sdk, I want to use 3 shunt current sensing method.

I don't want to add shunt resistor more in hardware to read battery current.

Could anyone tell me how to read battery current from 3 shunt resistors ? (low side 3 shunt current reading topology)

I don't want to mix motor current and battery current.

Would it be correct to find battery current if I add 3 shunt resistors readings to each other ? Any other constant or formula is involved in finding battery current ? ( such as electrical angle, phase current rms etc... )

for a couple of days, I haven't been able to sleep properly because of thinking about this question.

I need Help PLEASE.

I appreciate anyone's answer and time.

Thank you so much...