The work is devoted to solving the problem of improving the configuration of passive Battery Thermal Management System (BTMS) in Electric Vehicles from the point of view of the rationality of its implementation. The BTMS configuration is understood as a set of physicochemical, thermal parameters of the PCM and design solutions of battery modules. To determine the rational configuration of the BTMS, the method of computer modeling using SolidWorks Flow Simulation was used. Two BTMS models were developed with different battery module layouts. The effect of adding graphite nanoparticles, carbon nanotubes, and aluminum oxide in paraffinic PCM on the thermal characteristics of an electric vehicle battery module with different thicknesses of composite PCM layers was investigated. The best results were obtained with a complex arrangement of a 2 mm thick composite PCM around the battery module and 4 mm thick PCM layers between individual batteries. The results of computer simulation show that the use of thin layers of composite PCM together with copper plates and a flat heat plate allows to reduce the temperature of the battery module by 27.33% with a minimum temperature gradient of 1.51 °C, which confirms the effectiveness of the corresponding BTMS configuration. The results of the work can be used in the design of BTMS to ensure the economy and stable operation of electric vehicles.