A Multistage Adaptive Charging Algorithm for Li-Ion Battery-Based EV Applications

With the increase of electric vehicles and lack of standardization in charging infrastructure, the variance in the charger cable length, battery health, and battery capacity can result in unevenness in the charging of lithium-ion batteries (LIBs), which increases the charging time and can deteriorate the battery’s health. Enabling adaptive charging of LIBs can accelerate the commercial application of electric vehicles (EVs). Charging of LIBs is critical and can be optimized to curtail the effective charging time. In this paper, a multistage adaptive charging strategy is presented for LIB-based EV applications to boost the SOC of the battery system in the shortest time. In the proposed charging strategy, initially, multiple pre-charge CC stages are employed to bring the battery out of the deep discharge state and to simultaneously calculate the resistances of the harness (line resistance), and the battery. These resistance values are then used to estimate the charging currents as the terminal voltage reaches the charging cut-off voltage to extend the charging process. The algorithm also employs the topping-up action based on battery SOC to overcome the loss incurred due to the self-discharge phenomenon of the batteries. The multistage adaptive charging algorithm is developed in Matlab/Simulink simulation environment and is tested and validated on a LIB-based electric two-wheeler system, and the charging results of the proposed strategy obtained are compared with the results of CC-CV and two-stage CC-CC strategies.