Current flow in and out of a battery pack is a key parameter in any battery management system, hence the need for a current sensor.

EV Current Sensors: The Basics
EV current sensors are basic components. They perform two major tasks. They help us to know how much energy we use. Also, the second task is avoiding overcurrents. Therefore, current sensors are a major sub-systems of a battery design.
EV current sensors can include resistive or magnetic elements based on their structure. We use these elements for sensing the current to be measured. Thus, current sensor manufacturers make current sensors as two separate electrical paths: one is for the measurement current, the other one is for the signal conditioning.
Manufacturers
There are a number of different types of current sensor, different ranges and operating conditions.