Li-Ion Battery Pack Thermal Management: Liquid Versus Air Cooling

The Li-ion battery operation life is strongly dependent on the operating temperature and the temperature variation that occurs within each individual cell. Liquid-cooling is very effective in removing substantial amounts of heat with relatively low flow rates. On the other hand, air-cooling is simpler, lighter, and easier to maintain. However, for achieving similar cooling performance, a much higher volumetric air flow rate is required due to its lower heat capacity. This paper describes the fundamental differences between air-cooling and liquid-cooling applications in terms of basic flow and heat transfer parameters for Li-ion battery packs in terms of Q_ITD (inlet temperature difference). For air-cooling concepts with high Q_ITD, one must focus on heat transfer devices with relatively high heat transfer coefficients (100–150 W/m²/K) at air flow rates of 300–400 m³/h, low flow induced noise, and low-pressure drops. This can be achieved by using turbulators, such as delta winglets. The results show that the design concepts based on delta winglets can achieve Q_ITD of greater than 150 W/K.