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
Module End Plate Design
Meaning
Rigid structural brackets located at both ends of a battery cell stack hold the components together under pressure. Engineering teams optimize the module end plate design to resist the swelling forces of the cells over years of operation. These plates prevent the outer cells from expanding and keep the internal pressure within the target range.
They are usually made from high-strength aluminum alloys or reinforced plastics, and they must insulate the cell terminals electrically while resisting mechanical forces. This double role dictates the selection of both the base metal and the insulating coating.
Structural Requirement
Bending forces from swelling cells are highest at the center of the plate. A strong module end plate design utilizes reinforcing ribs or curved geometry to minimize deflection. Reducing this deflection prevents the failure of the long tension rods that bind the module together.
Excessive deflection can also break the busbar welds.
Mass Optimization
Adding thickness to structural parts increases vehicle weight and reduces energy density. Achieving a lightweight module end plate design involves removing material where stresses are low. Finite element analysis identifies these regions of low stress.
Sourcing teams select materials that offer a high strength-to-weight ratio.
Fastening Integration
Securing the module to the main battery pack tray requires integrated mounting points. The module end plate design often includes threaded holes or mounting ears to hold the module against high vibration loads. These mounting points must transfer the inertial loads of the heavy cells directly to the chassis of the vehicle.