Analysis and design of battery thermal management under extreme fast charging and discharging

Abstract

Thermal management is critical for the safety of electric vehicle (EV) battery packs, especially under ultra-fast and extreme fast charging and discharging use conditions. Liquid cooling is particularly attractive over other battery thermal management technologies due to its high heat transfer coefficient and low power usage. This paper systematically studies a liquid-cooled battery thermal management system for limiting the maximum temperature and voltage excursions of a standard 18650 lithium-ion battery pack. Considering two different coolant flow configurations, the influences of coolant flow rate, inlet temperature, battery capacity, charge rate, and discharge rate are investigated through a detailed computational study. Based on the simulations, design windows are developed for keeping the maximum temperature during charging below 45 °C and during discharging within 60 °C, as well as maintaining the cell voltage < 4.2 V. The design windows provide the maximum charge and discharge rates that can be achieved with a given coolant flow rate and inlet temperature for a battery capacity. Equivalently, the design windows may be utilized for a desired charge and discharge rate to obtain the required coolant flow design. The study provides valuable insight into advancing the ultra and extreme fast charge and discharge capabilities of battery packs for EV applications.