Battery Module Housing Mechanical Tolerances and Stack Calculations
Calculated worst-case and RSS mechanical stack tolerances govern inter-cell compression, housing deflection, bolt torque retention, and production assembly yield
Prismatic Cell Dimensions
Meaning
Height, width, and thickness specifications of hard-case rectangular battery cells dictate the volume available for active chemistry. Quality engineers verify the prismatic cell dimensions to ensure that the cells fit within the structural frame of the battery module. These measurements include the terminals, the vent height, and the expansion of the broad faces.
Even small deviations can cause assembly interference, which increases the scrap rate during the automated assembly step. Proper dimensioning is essential for high-throughput automated lines.
Outer Geometry
Metal cans hold the jelly roll in a rigid rectangular format. Fluctuations in prismatic cell dimensions occur due to variations in the deep drawing process during can manufacturing. Accurate thickness measurements must be taken when the cell is both fully charged and fully discharged.
These numbers form the basis of the module layout.
Assembly Tolerance
Stacking many cells in series multiplies the deviation of each individual component. Sourcing teams use prismatic cell dimensions to calculate the clearance needed inside the module enclosure. Using tight manufacturing tolerances prevents the total length of the stack from exceeding the capacity of the end plates.
This prevention avoids the need for manual sorting.
Sourcing Constraint
Industrial standardization of cell formats helps decrease the cost of battery packs. Standardized prismatic cell dimensions allow automotive manufacturers to source cells from multiple vendors without redesigning the module housing. This flexibility reduces supply chain risk and lowers the initial tooling cost.
It also simplifies the recycling process.