This paper reports a modeling approach for the scale-up of a lithium-ion polymer battery (LIPB). A comparison of the experimental discharge curves with the modeling results confirmed that the parameters used to model a small-scale LIPB could be applied to a large-scale LIPB provided the materials and composition of the electrodes as well as the processes for manufacturing the batteries were the same. The potential and current-density distribution on the electrodes of a LIPB were predicted as a function of the discharge time using the finite element method. In addition, the temperature distributions of the LIPB were calculated based on the modeling results of the potential and current-density distributions. The temperature distributions from the model were in good agreement with the experimental measurements.