AbstractThe battery thermal management system (BTMS) plays an important role in maintaining the optimal working temperature range and temperature uniformity of batteries. In this study, a novel liquid cooling BTMS for a cylindrical 21700-type battery is proposed. It uses straight microtubes and heat conduction blocks with a variable contact surface. An orthogonal test and multifactor analysis are used to determine the primary and secondary effects of the key structural and operating parameters on the cooling performance of the battery module. The results indicate that the working condition parameter of the BTMS, i.e., the liquid coolant flow rate (q), has a greater impact on the temperature performance of the batteries than the structural parameters [including the variable contact angle (Δα) and height (h) of the heat conduction blocks and the diameter of the straight microtubes (d)]. Δα is the most important structural parameter and has a significant influence on the temperature uniformity of the batteries. In the optimal combination model, Δα is 12°, h is 52 mm, d is 2.0 mm, and q is 0.2 L/min. Under these conditions, the maximum temperature and the maximum temperature difference are 34.6°C and 2.9°C, respectively, at the end of the 2C discharge cycle.