Feature: Power
EV battery pack
Battery packs Several diff erent cell types are used in EV batteries, including cylindrical, pouch and prismatic variants. T e one thing they all have in common is they are connected by busbars to form a battery module. T e prime objective when creating electrical connections is to ensure that the joint has low electrical resistance. T is minimises any energy loss through resistance and the resultant thermal heating, keeping the temperature of the pack as low as possible in operation, for best effi ciency. T e size of a weld has a direct eff ect on its electrical resistance,
and using laser technology enables uniform-size welds that consistently meet manufacturing specifi cations. Furthermore, the precision of the weld location and its depth are also crucial; for cylindrical cells, laser welding integrates real-time weld measurement that controls weld depth and other key parameters. T e materials used to manufacture the battery module,
whether the busbar or the battery cells themselves, are sensitive to imperfections. T e fact that laser welding is a non-contact process eliminates the risks associated with traditional methods such as resistance welding. Any imperfections leſt on the components as a result of the welding process can negatively impact the battery’s electrical performance and, ultimately, the electric vehicle itself.
Repeatable and fast The tight process controls used for laser welding make the busbar welding process repeatable and fast. Furthermore, the processing consistency achieved through a combination of control software and precision motion platforms enhances laser power stability, which in turn helps eliminate weld variations – a crucial factor in busbar welding. The high uptime, reliability and on-demand
availability offered by laser welding significantly improves productivity when compared with other, more conventional processes, which use consumables and often require greater levels of preventative and scheduled maintenance. In addition, the ability to re-program weld positions and parameters to cater for different product variants or module designs ensures future-proofing of the initial capital investment in the technology. Thanks to the ease of programming and high
repeatability, laser welding is also considerably faster than other, more traditional methods. For cylindrical cell batteries with thousands of connections, this higher speed equates to significant production cost savings.
www.electronicsworld.co.uk February 2024 31
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