A Li-ion battery charger based on remaining capacity with fuzzy temperature control

Abstract

Using high C-rate currents to charge batteries will cause large electrochemical reaction stresses, and thus result in high temperature rise and aggravate battery aging. To alleviate the battery aging and extend the life cycle, a remaining capacity (RC) charge method with fuzzy temperature control is proposed in this paper. According to the derived relationship between the charge C-rate and the state of charge (SOC) of the battery, a corresponding coarse-tuning charge current is determined. To control the temperature rise for subduing the aging effect, a fuzzy temperature controller (FTC) is designed to generate an incremental charging current to fine adjust the charge current. Following the charging progresses, by combining the fine-tune current with the coarse-tuning current, the studied charger can provide the adaptive charge current to charge the battery at any time. The synchronous-rectified buck converter is utilized to implement the charger. The firmware of the adaptive RC charging algorithm is realized by a microcontroller unit. Experimental results are given to verify the correctness and effectiveness of the proposed approach. Comparing to the conventional constant current-constant voltage (CC-CV) method, the proposed charging method reduces 23.2% of average temperature rise and increases 2.06% charge efficiency while maintaining similar charging time.