The Impact of Current Measurement Offset Error in SOC monitoring of HEVs


Monitoring of State of Charge (SOC) in Hybrid Electric Vehicle (HEV) batteries is important for maintaining operation of the battery within the manufacturer’s specifications for Depth of Discharge (DOD). Adherence to such specifications is important for the longevity and health of the battery pack as well as for the fuel consumption of an HEV. Because HEV batteries operate in a narrow SOC window (typically between 40-60% SOC), differences in voltage in this window can be small, making it difficult to use voltage measurement for determination of SOC with a reasonable level of accuracy. Further, voltage measurements cannot provide trustworthy information while the vehicle is in operation. Therefore, the battery management system (BMS) must rely on Coulomb counting through the current measurement system to determine SOC.

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