Integrated All-Climate Heating/Cooling System Design and Preheating Strategy for Lithium-Ion Battery Pack

The continuous low temperature in winter is the main factor limiting the popularity of electric vehicles in cold regions. The best way to solve this problem is by preheating power battery packs. Power battery packs have relatively high requirements with regard to the uniformity of temperature distribution during the preheating process. Aimed at this problem, taking a 30 Ah LiFePO4 (LFP) pouch battery as the research object, a three-sided liquid cooling structure that takes into account the preheating of the battery module was designed. On the basis of analyzing the influence of the cooling plate arrangement, cooling liquid flow rate, liquid medium, and inlet temperature on the temperature consistency of the battery module, the orthogonal simulation method was used to formulate the optimal combination of factors for different cooling objectives. Using the designed preheating structure, a combined internal and external preheating strategy based on the available battery power is proposed. The research results show that the cooling plate arrangement scheme and the inlet temperature have obvious influences on the preheating effect, while the increase in the flow velocity of the preheating effect is saturated. The optimized external preheating structure can maintain the preheating temperature difference of the battery module at less than 5 °C. On this basis, the proposed combined internal and external preheating strategy saves 50% of the preheating time compared with three-sided preheating.