Method for evaluating the accuracy of state‐of‐charge (SOC)/state‐of‐health (SOH) estimation of BMSs

Abstract

AbstractThe battery management system (BMS), which is widely adopted in various eco‐friendly automobiles that use batteries for propulsion, increases energy efficiency and extends the usable life by monitoring and optimally managing batteries. Eco‐friendly automobile original equipment manufacturers demand improvements in state‐of‐charge (SOC) and state‐of‐health (SOH) accuracies. However, because standards for evaluating accuracy do not exist, evaluations are performed using methods suggested by BMS developers or researchers, which differ from each other. Thus, the reliability of the SOC and SOH accuracy results is low. To accurately evaluate the SOC/SOH, it is necessary to reflect various conditions such as the power of the battery during actual vehicle operation and the temperature inside and outside the battery at the time. Therefore, a method is proposed herein that individually or simultaneously evaluates the SOC and SOH estimation accuracies of the BMS while considering an eco‐friendly vehicle's actual driving environment, instead of simple charge and discharge test conditions and room temperature. The reference values for evaluating the accuracy of SOC/SOH estimation in a battery can be defined as follows: Full charge and full discharge are conducted before applying the evaluation pattern to calculate the precise available capacity of the battery. Subsequently, it is fully charged and discharged to its initial SOC. A load pattern reflecting the load conditions of the subsequent application is repeatedly applied. After concluding the evaluation pattern, the remaining capacity is discharged, thereby determining the reference value. The proposed method is applied to two types of BMSs to evaluate its accuracy in SOC/SOH estimation and the validity of the proposed method was verified.