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BATTERIES & CHARGERS
LASERS ENHANCE PRODUCTION OF ELECTRIC VEHICLE
BATTERY CELLS As the transition away from internal combustion engines to electrically powered vehicles and hybrids continues to gather pace, manufacturers are not only supporting the market by designing and building new models, they are also having to completely rethink and re-structure some of their manufacturing processes. Although fewer traditional mechanical components are required within the drive train, this is offset by a significant increase in the demand for cables, harnesses, connectors, busbars and of course the all-Important battery packs needed to deliver the motive power. A key process in the production and assembly of EV battery packs is that of welding, and this is where the power, precision and flexibility of the laser ensures safe, consistent, and reliable connectivity.
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attery packs for electric vehicles comprise of multiple individual battery cells that are physically joined together and electrically connected. Producing these connections presents a number of challenges for
manufacturers, including the fact that there is often a combination of different thin, highly conductive materials of varying thicknesses which need to be joined, whilst ensuring there is no damage to the assembly as a result of any thermal or mechanical shock. A further challenge for manufacturers of EVs is that of overall weight, and whilst lightweight materials and composites can play an important role in reducing the weight of the vehicle structure, there is also an increasing use of lightweight aluminium in the current conducting elements of EVs such as the cables and busbars. In the past, the use of aluminium had been somewhat restricted due to difficulty in welding using conventional joining technologies. However, recent advances in laser welding now enables a greater use of aluminium for both current-conducting and structural components. Laser welding delivers precise, measured, and localised heat input, and the advanced process control and resultant consistency from the process makes it possible to achieve 100 per cent good welds. There are a number of different cell types used in the manufacture of EV batteries
including cylindrical, pouch and prismatic variants. The one thing that they all have in common is the fact that they need to be connected by busbars to form a battery module. The prime objective when creating electrical connections is to ensure that the joint has low electrical resistance. This minimises any energy loss through resistance and resultant thermal heating, keeping the temperature of the pack as low as possible when in operation to maintain the highest levels for efficiency of the battery pack. The size of a weld has a direct effect on electrical resistance and the use of laser technology makes it possible to produce welds which consistently meet manufacturing specifications, and which are also of a uniform size. Furthermore, the precision of the weld location and weld depth penetration are critical factors, and for cylindrical cells, laser welding solutions integrate real-time weld measurement which controls weld depth and other key welding parameters. The materials that are used to manufacture the battery module, whether for the busbar or the battery cells, are sensitive to imperfections. The fact that laser welding is a non-contact process eliminates the risks associated with traditional methods such as resistance welding. Any imperfections left on the components as a result of the welding process could have a negative effect on the electrical performance of the battery module and ultimately the electric vehicle itself.
The tight process control used for laser welding makes the busbar welding process repeatable and faster. Furthermore, the processing consistency achieved through a combination of control software and precision motion platforms enhances laser power stability, which in turn helps to 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 to other more conventional processes, which use consumables and often require greater levels of preventative and scheduled maintenance. In addition, the ability to be able to re-programme weld positions and parameters to cater for different product variants or module designs ensures futureproofing of the initial capital investment in the technology. Thanks to the ease of programming and high repeatability, laser welding is considerably faster than other more traditional methods. For cylindrical cell batteries with thousands of connections, this higher speed equates to significant production cost savings. The technologies and processes described here are just a small part of the comprehensive range of laser technologies and solutions available from Bromsgrove based TLM Laser.
TLM Laser
www.tlm-laser.com
Autumn 2023 UKManufacturing
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