Modeling Temperature Development of Li-Ion Battery Packs in Hybrid Refuse Truck Operating at Different Ambient Conditions

This paper presents a dynamic model for simulating the heat dissipation and the impact of Phase Change Materials (PCMs) on the peak temperature in Lithium-ion batteries during discharging operation of a hybrid truck under different ambient temperatures. The study aims to eliminate the electrical systems used for heating batteries in low temperature ambient and to replace the current active cooling systems with passive cooling, using PCMs, in high temperature ambient. The model is constructed by coupling a one-dimensional model of the electrochemical processes with a two-dimensional model for the heat transfer, including PCM implementation in a cross section of a rectangular LiFePO4 battery pack array. Two different cases are studied and compared, one when air is used (active cooling) and one when PCM is used (passive cooling). The results show that when the ambient temperature is the same as the initial temperature, the temperature drops when PCMs are used. For a higher ambient, the difference between active cooling and passive cooling is very low. For a low ambient, the PCM is not efficient for keeping the temperature at a safe temperature. This makes the use of PCM unpractical under low ambient conditions. Moreover, for a low current discharging process operating under high ambient temperature, an important nonuniformity appears inside the cell which can deteriorate the cells.