Optimal fast charging strategy for series-parallel configured lithium-ion battery packs without lithium plating

The limited charging performance of lithium-ion battery (LIB) packs has hindered the widespread adoption of electric vehicles (EVs), due to the complex arrangement of numerous cells in parallel or series within the packs. Despite the extensive research dedicated to optimizing the charging process for single cells, control strategies for packs remain unexplored. This paper focuses on the battery pack, employing a refined electric-thermo-aging coupled model for each cell to obtain external and internal dynamics. An application-oriented fast charging approach that integrates an extended Kalman filter (EKF) observer and a proportional-integral-derivative (PID) controller is proposed to achieve remarkable charging performance while mitigating lithium plating. This novel strategy has been validated on a commercial battery pack configured in three-parallel six-series (3P6S), showing an impressive charged capacity increase of 39.2 % in just 10 mins and 92.2 % in 53 mins at 25 degrees C, surpassing previous charging protocols. Impacts on pack parallel and serial branch resistances on pack charging performance are also investigated. For onboard application, simulation is extended to a real-world 58.8 kWh EV comprised of 276 cells, reducing the time to replenish 200 km of range to merely 12.5 mins. The insights from this research not only pave the way for efficient, damage-free fast charging of battery packs but also profoundly advance the practical application potential in actual vehicles.