What does a battery current sensor do

FAQ | Feb 23,2023

The battery current sensor is an amp clamp that measures current flow into and out of the battery. The current sensor then translates flow into a variable duty cycle signal. The sensor then sends this variable duty cycle to the BCM to indicate current flow.
Many modern cars have a battery current sensor. It might also be called a battery management or monitor sensor, or simply a battery sensor. Often, it is installed on the negative battery terminal or on the cable. Battery current sensorFord battery monitor sensorIn some cars, it might be installed on the positive terminal. Some cars have two battery sensors, one on each terminal.
How the battery sensor works: it measures the current to and from the battery. The sensor may also monitor the voltage, state of charge and state of health of the battery (aging). In some cars, it even measures the temperature of the battery.
The vehicle computer (BCM or PCM) uses these inputs to precisely adjust charging system voltage, idle speed and other parameters for better fuel efficiency and longer battery life. This system is called Power or Battery Management System or BMS. If the system detects that the battery is getting weak, it may turn off some electrical accessories (load shedding), such as the navigation, heated steering, heated seats, etc., to save the battery power. In this case, the computer will display a warning message on the instrument panel.
The function of the battery sensor is particularly important in vehicles with Stop-Start feature, as the battery management system must verify that the battery has enough charge to re-start the vehicle. If the battery is low on charge, the Stop-Start feature is disabled. The charging system current is also often higher in vehicles with Stop-Start feature. For this reason, in some vehicles, if the sensor has been disconnected or the battery has been replaced, the Stop-Start feature might not work for some time, until the computer (BCM or PCM) re-learns the parameters of the battery.


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