The development of a comprehensive battery simulator is essential for future improvements in the durability, performance and service life of lithium-ion batteries. Although simulations can never replace actual experimental data, they can still be used to provide valuable insights into the performance of the battery, especially under different operating conditions. In addition, a single-cell model can be easily extended to the pack level and can be used in the optimization of a battery pack. The first step in building a simulator is to create a model that can effectively capture both the voltage response and thermal behavior of the battery. Since these effects are coupled together, creating a robust simulator requires modeling both components. This paper will develop a battery simulator, where the entire battery model will be composed of four smaller submodels: a heat generation model, a thermal model, a battery parameter model and a voltage response model. The paper will provide a brief description on each of these four sub-models and how they are correlated with each other. In addition, this work will examine the significance of accounting for the reversible heat generation term when predicting battery temperature.The obtained comprehensive model will then be validated by testing on a 20 Ah lithium iron phosphate battery. The results show that the electro-thermal model can adequately capture both the voltage and thermal trends in the battery. In addition, the findings indicate that accurate tracking of the curvature present in the temperature profile during discharge/charge can only be accomplished by including the reversible heat generation component in the overall model. These findings are beneficial for battery design and optimization in future applications.