The need for powering portable equipment and electric vehicles has resulted in an intense battery development program. The resulting electrochemical systems deliver over 100 watthours per kg of battery mass. Achieving this high energy-density in the new batteries requires separating the structural and current-carrying components from the electrochemical components, and optimizing their design. Building these lightweight, high-performance cells requires a sophisticated manufacturing process that must be precisely controlled. For example, lithium, an anode in lightweight cells, is also very combustible, and a comprehensive test program is required before any lithium cell is introduced to the market to assure that under no conceivable condition will the cell start a fire. Thus every manufacturing step must be monitored. In this paper we describe a new tool, pressure-indicating film, that is being used in controlling manufacturing steps.