In this study, numerical models of an active thermal management system (TMS) using a two-phase refrigerant and a passive TMS using phase change material (PCM) for lithium ion batteries in electric vehicles (EVs) and hybrid electric vehicles (HEVs) are developed. The models are validated by comparing the predictions with the measured data. The effects of the refrigerant temperature and mass flow rate on the cooling performance of the refrigerant-cooled active TMS are analyzed. Moreover, the cooling performance characteristics of the refrigerant-cooled active and PCM-based passive TMSs are compared under various single discharge and cyclic operating conditions. The passive and active TMSs show excellent performances under mild and stressful operating conditions where discharge occurs. However, in the cyclic operation where charge and discharge are merged, the refrigerant-cooled active TMS shows better cooling performance than the PCM-based passive TMS. (C) 2019 Elsevier Ltd. All rights reserved.