An air-cooled system with a control strategy for efficient battery thermal management

Air-cooled systems are widely used in electric vehicles for the thermal management of battery packs. Due to the low specific heat capacity of air, design of air-cooled systems is required to improve the temperature uniformity of battery packs. However, structural design of the system cannot meet the requirement of battery thermal management under varying operating conditions. In this study, a parallel air-cooled system with a control strategy is developed for efficient cooling of battery packs under varying operating conditions. The performance of the air-cooled systems with different single flow types is investigated numerically, with the results verified by experiments. A control strategy based on the temperature difference among battery cells is proposed for the system with J-type flow, and the mechanism by which traditional systems fail in temperature difference control is revealed. To address this issue, an efficient thermal management system that integrates different flow types is proposed and relevant control strategy is developed, with decreased widths of the parallel channels on both ends. The proposed system with the control strategy reduces the temperature difference among battery cells by switching the flow type on demand and guiding more cooling air to the battery cell with high temperature. The numerical results of the cases with high current discharge rate and with varying random operating conditions show that the developed system enables the temperature difference to be controlled below 0.5 K after several switches of flow type. The average temperature difference among the battery cells in the developed system is reduced by more than 67% compared to that with J-type flow alone. The proposed system with the relevant control strategy is efficient for thermal management of battery packs under varying operating conditions.