Effect of Fast Discharge of a Battery on its Core Temperature

In this paper, results of a simulation carried out to estimate the core temperature (Tc) of a Lithium ion (Li) battery for various C rates and a standard drive cycle FTP75 using MATLAB / Simulink are presented. A mathematical model of a charger was developed by integrating a SEPIC with a Li ion battery. The SEPIC was modeled using governing volt sec and amp second balance dynamic equations and was supplied to the battery of nominal capacity 40Ah. A thermal model of the battery was developed to investigate Tc, based on measured ambient (Tamb) and surface (Ts) temperatures. It was found Tc increased during the discharge process and the difference between Tc and Ts increased to large values as the C rate increased. With the proper estimation of Tc, efficient thermal management can be achieved. Hence, the State of Health (SOH) for a battery during fast discharging and charging can be monitored effectively, thus enabling development of an efficient and safe Battery Management System.