State of health estimation of lithium-ion batteries based on the constant voltage charging curve

Abstract

State of health estimation is critical for ensuring the safety and dependability of lithium-ion batteries. In practical usage, batteries are seldom completely discharged. With a constant current-constant voltage charging mode, the incomplete discharging process influences the initial charging voltage and the charging time of the subsequent constant current charging, greatly hindering the applications of many traditional health indicators that require a full cycling process. However, the charging data of the constant voltage charging is fully reserved, and is not affected by the previous incomplete discharging process. Furthermore, the charging current curve during the constant voltage profile is discovered to relate with the battery state of health in this study. Therefore, a new health indicator is extracted only from the monitoring parameters of the constant voltage profile for state of health estimation. The battery aging phenomena during the constant voltage profile are firstly characterized by the equivalent circuit model, and a new indicator is then constructed. A framework for the online extraction of this indicator of is proposed. Additionally, the correlation analysis and performance assessment prove the adaptability and effectiveness of the proposed method for estimating state of health of lithium-ion batteries.