A Constant-Temperature Fast Charging Strategy Based on Multiclosed-Loop Control for Lithium-Ion Batteries

Abstract

Fast charging technology is recognized as the enabling technology to promote the large-scale popularization of electric vehicles (EVs). However, the high-rate fast charging can lead to a rapid rise in battery temperature, triggering safety accidents such as rapid degradation of battery capacity or even thermal runaway. Inspired by this, a constant-voltage constant-temperature (CVCT) fast charging strategy is proposed to maximize the charging speed. Especially, a temperature control loop has been added to the previous constant-current constant-voltage (CCCV) charging strategy. Numerous tests have been performed for lithium-ion batteries. The experimental results show that the proposed strategy can charge the battery state of charge (SOC) from 0% to 80% in as little as 4.90 min. The charging speed is 32.8% faster than the conventional CCCV strategy and 23.1% faster than the deep reinforcement learning (DRL)-based strategy under the same temperature limit. Given the similar charging speed, the temperature rise is 35% lower than the traditional CCCV charging strategy, and the cycle life is extended by about 49.5%. Moreover, the CVCT charging strategy is highly adaptive to the environmental temperature and the initial charging state, which ensures its robust performance in real applications.