Hybrid Electric Vehicles (HEV) are considered to be a viable solution for the sustainability of the planet from global warming.  phase change materials (PCM) are proved to be an efficient way to manage the thermal systems such engines as PCM has a high latent heat storage capacity and this removes the heat from the battery providing an opportunity for the battery to run for longer durations without experiencing runaway propagation. , the main objective of this study is to investigate the copper fin influence in a PCM cooled HEV engine using numerical investigation where the Rubitherm Paraffin (RT 58) was used as the PCM. The study found that the cooper fin has a positive influence on cooling efficiency