Design of batteries for automotive applications requires a careful balance between vehicle requirements - as driven by automakers - and cost. Typically, for batteries, the goal is to meet the most stringent requirement at a competitive cost. The real challenge in doing so is understanding how the battery-level requirements vary with changes in the vehicle, powertrain, and drive cycle.In this work, we consider the relationship between vehicle-level and battery-level requirements of microhybrid vehicles and their linkage with battery design. These vehicle platforms demand high-power pulses for impractical durations - over 60 seconds on some drive cycles.We demonstrate a method for optimizing the battery design for fuel economy against any specific drive cycle, whether regulatory, consumer, or otherwise. This method allows for a high degree of customization against manufacturer or consumer value. Electrochemical modeling and vehicle modeling, coupled with experimental validation, is used to investigate the effects of key battery design parameters - such as particle size and coating thickness - on the energy and power capability of lithium ion batteries.