A Fast Charging Method for Lithium-ion Batteries Considering Charging Urgency of the User

Fast charging of lithium-ion batteries (LIBs) is a key technology for the popularization of electric vehicles. However, regardless of physical constraints, high-rate charging will accelerate the decline of battery capacity. There is a contradiction between charging speed and cycle life. Motivated by this, this paper defines the user's charging urgency factor for the first time and transforms it into the charging safety constraints. On this basis, a fast charging strategy is proposed, which can automatically select the charging rate based on the user's charging urgency. In particular, a state-of-the-art Twin Delayed Deep Deterministic (TD3) deep reinforcement learning (DRL) algorithm is exploited to determine the fast charging strategy, and the electrochemical-thermal-aging coupling model is introduced to train the strategy. The well-trained strategy can charge the battery state of charge (SOC) from 0% to 80% in as little as 7.33 minutes. The average charge time is 13.11 minutes and the average cycle life is 3158 times, achieving the balance between charging speed and cycle life in the whole battery life. In addition, the proposed charging strategy extends the cycle life by 35% over the CCCV charging protocol and increases the speed by 26% over the MCCCV charging protocol.