This article experimentally investigates the heat generation characteristics and the effectiveness of passive cooling of commercially available LiFePO 4 (7.25 mm × 160 mm × 227 mm, 19.5 Ah) cells using different cooling materials. The specific heat capacity and the entropy coefficient of the cell are experimentally measured. The heat generation rate of the cell at 1-4 C current rates are also determined using three different methods: (1) the heat absorption calculated from the temperature increase of cooling water; (2) the energy loss calculated from the difference between the operating voltage and open circuit voltage; and (3) the energy loss during a charge-discharge cycle calculated using the voltage difference between charging and discharging. Results show that the heat generation rate estimated from heat absorbed by the water can be underestimated by up to 47.8% because of the temperature gradient within the cell and on the surface. The effectiveness of different passive cooling materials is compared at discharge current rates of 1-3 C. The average increase of the cell surface temperature is 22.6, 17.1, 7.7, 7.2 and 6.4 • C at 3 C (58.5 A) using air, aluminum foam, octadecane, water with aluminum foam and water, respectively.

This investigation into phase change material (PCM)-based passive thermal management systems was conducted via an experimental approach using 19.5 A h lithium iron phosphate cells with dimensions of (7.25 × 160 × 227) mm3. Trials were conducted at currents from 1 to 5C and environmental temperatures from 4 to 35 °C to simulate applications at which a Li-ion battery would be expected to perform. Based on comparisons, including an air-only control, the system consisting of PCM combined with five pores per inch (PPI) aluminum foam is the most effective at regulating average battery temperature and temperature gradient. During a 3C discharge trial at room temperature, the PCM-Al foam (5 PPI) system kept the average battery temperature and the maximum temperature difference below 28.1 and 5.2 °C, respectively, compared to the air-only control system which reached values of 48.0 and 17.2 °C, respectively. When analyzing data from trials at 4 and 35 °C, similar results are found with the PCM-Al foam systems being effective at thermal management. Thus, when compared to other systems, preliminary results show great promise in the future for the use of an PCM-Al foam passive thermal management system to effectively regulate the temperature of Li-ion batteries during use.