Battery voltage modeling for portable systems

Limited battery life imposes stringent constraints on the operation of battery-powered portable systems. During battery discharge, the battery voltage decreases, until a certain cutoff value is reached, marking the end of battery life. The amount of discharge capacity and energy delivered by the battery during its life depends not only on the battery characteristics, but also on the load conditions. A different system design may result in a different battery current (load) profile over time, leading to a different battery voltage profile over time. This article presents an analytical model that relates the battery voltage to the battery current, thus facilitating system design optimizations with respect to the battery performance. It captures well-known nonlinear phenomena of capacity loss at high discharge rates, charge recovery, and capacity fading. The proposed model has been validated against measurements taken on Li-ion batteries. We also describe techniques for efficient calculations of model's estimates, which lets a user exploit accuracy-complexity tradeoffs.