In this study, thermal management of battery module is investigated using PCM nanocomposite filled in the gap between the cells. The PCM nanocomposite consists of eicosane as PCM and silver nanoparticles as TCE. The proposed thermal model takes into account the joule as well as entropic heating which is neglected in most of the existing research works. The heat transfer in PCM nanocomposite and cells are modeled by solving the energy transport equation and the phase change in PCM is modeled using the popular enthalpy method. Conduction with heat generation is considered in the battery cells and conduction dominated phase change is considered in the PCM nanocomposite regions. Finite volume based numerical model is used to solve the governing energy transport equations for cells and PCM nanocomposite regions. Implicit source based enthalpy method is used to capture the transient evolution of solid-liquid phase front. The proposed model is validated with the available experimental results. It is found that with increased percentage of high conductivity nanoparticles in the PCM, the battery cells temperatures decreases significantly with enhanced melting of PCM.