Experimental Studies on Li-ion Battery Pack for Temperature Distribution Analysis During Fast Discharging and Various Ambient Temperature Conditions

Lithium-ion batteries are the primary energy source for electric vehicles (EVs), which were developed to address environmental issues and the lack of energy resources. The temperature is a key factor in Li-ion batteries which affects their degradation and life span. In this study, the thermal performance characteristics of a 4S2P Li-ion battery pack are analyzed according to the change in the environmental temperatures of 25°C, 40°C, and 60°C and the discharge rates of 0.5C, 1C, 2C, and 3C of the battery. In the experiment, the maximum temperature rises in the battery pack at 0.5C discharge rate is within the optimum operation range with respect to all tested ambient temperature conditions. Meanwhile, it is higher at an ambient temperature of 25°C than at ambient temperatures of 40°C and 60°C during high-current discharge (1C, 2C, and 3C) operations. The results prove that the environmental temperature of 40°C provides better thermal performance than 25°C and 60°C operating levels. Also, the temperature distribution between neighboring cells in the pack increases as the C-rate increases from 0.5C to 3C, and this nonuniformity causing high heat generation can lead to a performance reduction of the module. This article primarily proposed a correlation between heat transfer and ambient temperatures in terms of discharge rate. The correlation is significant when designing thermal management systems for battery-powered devices.