Intelligent Battery Sensor (IBS)

The IBS serves two primary purposes. The first is to provide the PCM with both immediate and historical calculated battery information, so the PCM can precisely control the charging system. The second purpose is to provide calculated data to the BCM for operation of the load-shedding feature. A fused power circuit and the bus are connected to the IBS though a two-terminal connector.

The IBS contains a low value resistor, or shunt. The shunt creates voltage drop, which is read by an internal controller 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 communication bus to the BCM, which is the LIN master node of the IBS. In addition to real-time measurements, the IBS transmits some calculated battery data over the bus, including SOC, State of Health (SOH), and State of Function (SOF). These values are calculated by storing measurements over time.

• SOC = Battery 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 SOF is a calculated prediction of the lowest voltage the battery will drop to during engine cranking.

The battery sensor is readable and diagnosable by using the diagnostic scan tool which can display all of the available parameters needed for vehicle servicing or trouble shooting.

When the IBS is powered up for the first time or is powered after a battery disconnect, it enters a "recalibration" phase, where the IBS must recognize the type of battery and its characteristics and state. This information is sent to the IBS by the BCM. In this phase the tolerances on the state functions (SOC, SOF) are greater than in normal working condition. When the IBS is disconnected from the battery, the device loses its stored memory. When power is restored, the IBS starts a relearn process. Until the relearn process is complete, accurate battery state information is unavailable to other vehicle systems. The IBS relearn process requires one start and at least four hours of quiescent time (vehicle off, electrical system asleep). The relearn process is restarted every time power is reconnected to the IBS. This has a major effect on the Engine Start Stop (ESS) feature.