A modular energy storage device comprises a customer-defined parameter, such as electrical capacity, a can that has a dimension based on the customer-defined parameter, an electrode package that has properties based on the customer-defined parameter, and a header that has a configuration that is not dependent on the customer-defined parameter. A method for producing the modular energy storage device comprises generating a standardized energy storage device configuration, receiving a customer-defined parameter, and modifying the standardized energy storage device configuration according to the customer-defined parameter. The step of modifying the standardized energy storage device configuration comprises the steps of modifying the electrode package without modifying the location of the current collectors, modifying the length of the can according to the customer-defined parameter, and using the header already developed to complete construction of the modular energy storage device.