132 Chapter 11 automotive application, will it mount under the hood, in the passenger compartment, under the chassis, in the trunk? If stationary power application, will it be in a mobile enclosure or will it be permanently mounted? If a marine application, what sealing and environmental requirements will it have? Once we understand the location for the system installation, we can begin looking at the other requirements. Does it need to stand up against harsh environmental requirements? What level of sealing does it need to have? Is it a structural component in the system? What kind of shock and vibration will the system experience? Next we can evaluate the other mechanical needs.
Does it mount in a crash zone within the vehicle? Does it need to meet any knee loading requirements, in other words does it need to be able to stand up to someone standing or stepping on it? Additionally, we must evaluate other influences such as electromagnetic interference and electromagnetic compatibility impacts, the distance to other heat generating components in the vehicle, the distance to the passengers and the need for serviceability of the pack.
The components of the ESS that we are interested in here from a mechanical and structural perspective include the housing or enclosure within which ESS is installed and the mechanical structure that encloses and protects the cells, referred to as the module. Both of these components may include a combination of steel, aluminum, plastic, fiber glass, and composite materials. Understanding the level of shock and vibration that your ESS will experience is also a key aspect of your mechanical design. For instance, in automotive applications a high level of vibration resistance may be necessary. This may be accomplished through a combination of design and material selection.
In some cases, the designer may include a foam type of mate- rial in order to reduce the impact of the vibration on the battery pack. It is also vital that the flow of the vibration through the battery does not go through the cell and the cell interconnec- tions. The mechanical system design must account for this and isolate the cells and their connectors since this will cause increasing impedance, increasing levels of heat, and eventu- ally premature failure. For other systems such as may be integrated into very large systems, the impact of shock on the battery must be evaluated and accounted for in the design.
Module Designs Since we are talking about mechanical and structural components of the battery system, let us take just a moment to discuss the different types of battery modules that are in use today. The term battery module is generally used to refer to the assembly of lithium-ion cells into a single mechanical and electrical unit. The module consists of the lithium-ion cells, bus bars, voltage/temperature monitoring printed circuit board, thermal management components, and finally the overall mechanical structure. The module design will depend highly on a couple of things. First is the type of cell being used as this will necessitate the final design configuration.
For instance, the use of a