Adaptive Charging Strategy With Temperature Rise Mitigation and Cycle Life Extension for Li-ion Batteries

Abstract

Charging battery with a large Crate current to shorten the charging time (CT) will induce the drastic electrochemical reaction, and thus bring about the significant temperature rise (TR), energy loss, performance degradation, and safety concern as well. To tackle this problem, an adaptive charging strategy with TR mitigation and cycle life extension is proposed in this study. Based on the relationship between the charging current and remaining state of charge (RSOC) which is extracted experimentally, a baseline charging current is determined first. To control the temperature rise further, a fuzzy TR controller (FTC) is devised to fine-tune the charging current according to the temperature gradient. Thus an adaptive charging current with temperature rise suppression mechanism can be generated dynamically in the entire charging process. The proposed charging strategy is validated by means of experimental studies and compared with the conventional constant current-constant voltage (CC-CV) method. The results show that the average temperature rise, charging efficiency, and estimated cycle life have 31.24%, 2.06%, and 57.3% of improvement respectively as compared with that of the conventional CC-CV obtained. Index Terms-Adaptive charging strategy, cycle life extension, fuzzy temperature-rise controller. nomenclature CT Charging time. TR Temperature rise. SOC State of charge. RSOC Remaining state of charge. FTC Fuzzy temperature-rise controller. CC-CV Constant current-constant voltage. HEV Hybrid electric vehicle. EV Electric vehicle. ESS Energy storage system. Li-ion Lithium-ion. RCC Remaining capacity charging. 4S2P Four series two parallel. SBC Synchronous buck converter. MCU Microcontroller unit. GUI Graphic user interface. I 2 C Inter-integrated circuit. ADC Analog to digital converter. FIR Finite impulse response. PID Proportional integral differential. DPWM Digital pulse width modulation. CTR Charging time ratio. MF Membership function. UOD Universe of discourse. COS Center of sum. RCFTC Remaining capacity with FTC.

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