With the growing complexity of electrical and electronic subsystems on modern vehicle platforms, performance of the battery becomes an ever-increasing concern for the user and consequently a key technical focus for the developer. Detailed models are germane for accurate predictions and assured performance. Models should include parameters and variables for the multitude of conditions that affect the output. Whereas many traditional models only account for coulombic discharge capacities (i.e. amp-hours) a complete model must predict terminal voltage to provide for an accurate energy estimator. This aspect is most important as real-world performance is impacted by the mix of resistive and constant-power loads on the vehicle. In particular, constant-power loads will draw increasing amounts of current and/or run longer when the voltage is reduced. Using battery manufacturer data, a multi-dimensional model is provided. The model accounts for the previously mentioned variables as well as the internal thermal heating of the battery during discharge conditions.