Cylindrical Prismatic and Pouch Cells and How Packs Are Built
Cell format selection dictates pack thermal dissipation paths, stack compression mechanics, busbar welding tolerances, and compliance responsibility.
Tab Fatigue
Meaning
Mechanical failure modes characterized by the progressive cracking of terminal tabs under cyclic vibration cause electrical open circuits in battery modules. Sourcing teams evaluate tab fatigue during the cell qualification phase to ensure the long-term reliability of the electrical connections. This failure mode occurs when the thin metal strips that connect the cell electrodes to the busbars are subjected to mechanical vibration.
The boundary where this failure occurs is defined by the resonant frequencies of the battery pack and the amplitude of the vibrations.
Fatigue Mechanics
Vibration during vehicle operation or industrial use generates cyclic bending stresses on the connection tabs. These stresses lead to the initiation and propagation of micro-cracks at the bend radius or the weld interface. Over time, these cracks grow until the tab fractures, resulting in a sudden increase in electrical resistance or a complete open circuit.
This can trigger battery management system errors and shut down the entire pack. Sourcing managers must ensure that the cell design incorporates strain relief features to minimize the stresses on the tabs.
Vibration Testing
Testing protocols utilize shaker tables to subject the battery modules to sweep tests and random vibration profiles. These tests simulate the lifetime vibration exposure of the vehicle to verify the durability of the tabs. Sourcing agreements specify the testing duration and the acceptable post-test contact resistance.
Commercial Sourcing
Supplier selection is influenced by the mechanical design of the tab and the materials used. Nickel and aluminum tabs must be chosen with the correct hardness and thickness to balance flexibility and conductivity. Sourcing teams should audit the supplier’s testing laboratory to ensure they have the capability to perform high-frequency vibration testing on full-scale modules.
This reduces the risk of field failures and warranty claims.