Electrochemical Corrosion Kinetics across Dissimilar Conductor Interfaces
Electrochemical corrosion kinetics across dissimilar conductor interfaces accelerate through moisture condensation, demanding perimeter sealing and barrier plating.
Terminal Joint Fatigue
Meaning
Structural degradation occurs in the electrical connections between battery cells and busbars due to repeated mechanical and thermal stresses. Terminal joint fatigue is caused by the vibration of the vehicle and the expansion of the cells during the charge and discharge process. Over time, these stresses can lead to microscopic cracks that increase the electrical resistance and may eventually cause the connection to break.
Stress Driver
Mechanical loads from the road and the swelling of the cell modules are the primary contributors to this wear. Every time the battery is used, terminal joint fatigue progresses as the different materials in the connection expand at different rates. This thermal cycling is particularly intense during fast charging when the temperature rises quickly and the parts move relative to each other.
Failure Progression
Increase in contact resistance leads to localized heating which further accelerates the damage. As terminal joint fatigue worsens, the heat generated at the connection can become high enough to melt the surrounding plastic or damage the cell seal. This creates a feedback loop where the higher temperature leads to more movement and more cracking, eventually resulting in a complete open circuit.
The increased resistance can also interfere with the voltage sensing of the battery management system, leading to incorrect state of charge readings and potential overcharge of individual cells.
Design Mitigation
Engineering solutions focus on reducing the strain at the connection point through the use of flexible links. By incorporating expansion loops or braided wire, the effects of terminal joint fatigue can be minimized because the movement is absorbed by the flexible component rather than the rigid weld. This approach ensures that the battery pack can survive the hundreds of thousands of kilometers expected in a modern electric vehicle.