We perform heat transfer analysis of a thermal battery module for a high-power and large-capacity thermal battery system based on a detailed thermal model as well as an effective thermal model. Firstly, the transient thermal behavior of a small scale thermal battery module consisting of 13 stacks of unit cells is investigated by the detailed thermal model that considers every components. We show that the net effect of Joule heating (exothermic) and chemical reaction heat (endothermic) occurring in the unit cell result in different degree of cooling down the thermal battery depending on the operating condition. It is also found that anisotropic heat conduction due to the stacked geometry of the unit cell causes temperature non-uniformity within the thermal battery module. Secondly, we also develop an effective thermal model based on the properly averaged thermophysical properties of constituent materials of unit cells as well as the homogenized heat sources. The effective thermal model is validated by comparing it with the detailed thermal model for the small scale thermal battery module consisting of 13 stacks of unit cells, and it is further extended to the large scale thermal battery module consisting of 54 stacks of unit cells.