This paper reports a modeling methodology to predict the thermal behaviors of a lithium-ion battery (LIB) during constant-power discharge and charge operations. An efficient algorithm is presented to estimate the voltage and current of an LIB as a function of time in the mode of constant-power discharge and charge. The experimental discharge and charge curves at various power levels of 25, 50, 100, 150, and 250 W are compared with the modeling results to validate the two-dimensional modeling of the potential and current density distribution on the electrodes of an LIB cell during constant-power operations. The two-dimensional temperature distributions of the LIB cell as a function of time are calculated based on the modeling results of the two-dimensional potential and current density distributions. The temperature distributions obtained from the modeling agree well with the experimental measurements based on infrared imaging. (C) 2013 The Electrochemical Society. All rights reserved.