Sensor, Intelligent Battery (IBS): Operation

WARNING: This page is about a different car, the 2020 Chrysler 300 and 2019 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.

The Intelligent Battery Sensor (IBS) contains a low value resistor, or shunt. The shunt creates voltage drop, which is read by an internal microcontroller to determine the current flow in and out of the battery. In addition to the shunt, the IBS contains a sensor to monitor the battery's temperature. Data gathered by the IBS, including temperature, voltage, and current measurements, are transmitted over a LIN communication bus tor the Body Control Module (BCM). The IBS serves two primary purposes. The first is to provide the BCM with both immediate and historical battery information, so the PCM can precisely control the charging system. The second purpose is to provide data to the BCM for operation of the load-shedding feature. A fused power circuit and the LIN bus are connected to the IBS though a two-terminal connector.

In addition to real-time measurements, the IBS transmits some calculated battery data over the LIN bus, including state of charge, state of health, and state of function. These values are calculated by storing measurements over time.

The battery sensor is readable via a "scan tool" that can display all of the available parameters needed for vehicle servicing or trouble shooting.

Information the Intelligent Battery Sensor (IBS) transmits out on the CAN Bus is

SOC = Battery state of charge (SOC) is expressed as a percentage. The IBS calculates the SOC based on measured voltage, and charge and discharge rates. Therefore, SOC is not a direct percentage of battery voltage.
SOF = Battery State of Function: Battery state of function (SOF) is a calculated prediction of the lowest voltage the battery will drop to during engine cranking.

The BCM uses this calculated information to optimize vehicle power management for increased fuel efficiency. The data transmitted from IBS is interpreted and sent over the CAN network by the module connected the IBS's LIN bus.

When the IBS is powered up for the first time or is powered after a power disconnection, it enters a "recalibration" phase, where the IBS must recognize the type of battery and its characteristics and state. In this phase the tolerances on the state functions (SOC, SOF) are greater than in normal working condition. When IBS is disconnected from the battery, the device loses its stored memory. When power is restored, the IBS starts a relearn process. The IBS relearn process requires 3 to 5 normal starts with at least four hours of engine off time. Until the relearn process is complete, accurate battery state information is unavailable to other vehicle systems. Remember, the relearn process is restarted every time power is reconnected to the IBS.

If the IBS is faulty it cannot be serviced, it must be replaced.