Battery packs of electric vehicles are made up of a large number of single smaller lithium-ion cells. During discharge and charge, heat is generated inside the cell proportional to the square of the current due to the internal resistance of the cell. Nowadays, battery cells are imposed with increasing demands for power and volume density in order to obtain the highest possible performance of electric vehicles, but also to achieve charging time of electric vehicles similar to those seen in conventional vehicles with internal combustion engines. The lifespan and performance of lithium-ion cells depend significantly on the operating temperature and temperature uniformity between the cells. Conventional battery pack cooling methods are having difficulties with keeping up with the imposed increases in vehicle performance. Consequently, the battery cooling system is becoming a bottleneck for further performance improvements. For these reasons a need for a new battery cooling system is noticed. In this paper an experimental rig of a battery pack cooling system with two-phase cooling has been designed. In it, a liquid evaporates in direct contact with electrical cells. The first chapter deals with the problem of cell cooling and provides an overview of the most common ways of battery cooling in vehicles present on the market today. The second chapter gives an introduction to the two-phase cooling technique and presents the detected pumped two-phase systems and detected papers that describe battery cell cooling by evaporation of fluids in direct contact. The third chapter contains the development of an experimental rig model that would test the technique of two-phase cooling on a battery pack with 4 modules of 50 cells with an overview of potential liquids that could be used for those applications. In the fourth chapter, the main components of such an experimental rig are dimensioned and measuring equipment is selected that will enable accurate recording the of system parameters. In the fifth chapter, the calculation of the system pressure drop was performed. The hydraulic connection diagram of the test system is made and the disposition drawing of the experimental system is shown.