Thermal batteries are primary disposable systems specially designed to develop a high energy density in a short period. In the present work, the modeling of heat generation and propagation within three Ca/CaCrO4 thermal batteries has been carried out, using a transient model. The commercial CFD software Phoenics® has been used and, through a typical finite volume approach, the related 2D transport equations have been solved, giving the time-dependent temperature profiles. To check the quality of the model, the temperature of pseudo-equilibrium state (a typical thermodynamic parameter), has been analyzed. The temperatures related in the literature were close to those calculated. The results also indicate that the fusion of electrolytes is virtually an instantaneous process when compared to the time to reach the pseudo-equilibrium state, which indicates that the generation of electrical current occurs immediately after the thermite burning.