As the core of a vehicle's powertrain, the internal connection stability of the battery pack directly impacts the overall vehicle performance and safety. The copper busbar, a critical component in the battery pack responsible for high-current transmission, requires a collaborative approach to ensure connection reliability through material properties, structural design, and process control.
The inherent properties of the copper busbar provide the physical foundation for connection stability. Its high conductivity reduces energy loss during transmission, preventing connection loosening due to overheating; its high ductility allows for slight deformation without breakage during battery pack vibration or thermal expansion and contraction, a "flexible yet rigid" characteristic that enables it to adapt to complex operating conditions. Simultaneously, the naturally formed oxide film on the copper surface provides moderate insulation, preventing short circuits without excessive thickness leading to increased contact resistance—a balanced characteristic difficult for other metals to replicate.
In terms of structural design, the copper busbar employs a combination of modular layout and flexible connections. The modular design divides the battery pack into independent units, each connected in series or parallel via copper busbars, preventing localized faults from propagating to the entire system. Flexible connections utilize corrugated structures or pre-installed expansion gaps in the middle section of the copper busbar to absorb volume changes in individual battery cells during charging and discharging, preventing stress concentration-induced breakage. For example, some models employ an "S-shaped" copper busbar, maintaining conductivity while releasing mechanical stress through geometric deformation.
Welding is a core element ensuring the stability of the copper busbar connection. Laser welding technology, due to its concentrated energy and small heat-affected zone, has become the preferred choice for high-end vehicles. This process uses a high-energy laser beam to instantly melt the copper, forming a uniform molten pool. After cooling, a dense metallurgical bond is formed, with a connection strength approaching that of the base material itself. For complex structures, ultrasonic welding uses high-frequency vibration to cause metal atoms at the contact surface to diffuse, creating a "cold welding" effect and avoiding spatter and porosity defects that may occur with traditional resistance welding.
Regarding mechanical fastening, the connection between the copper busbar and the battery terminals employs a "double-locking" mechanism. First, a preset torque is applied using high-strength bolts to ensure initial contact pressure; second, elastic clips or springs are added to the connection area to compensate for creep relaxation during long-term use. This design ensures stable connection resistance throughout the vehicle's lifespan, preventing localized overheating caused by poor contact. Some models also embed temperature sensors at the connection points to monitor contact temperature rise in real time and provide early warnings of potential risks.
Insulation is a crucial aspect of copper busbar applications. In addition to using high-temperature resistant, flame-retardant polyimide or epoxy resin coatings, some designs also apply a conductive oxide layer to the copper busbar surface, maintaining conductivity continuity while forming an insulating barrier. For high-voltage systems, a metal shielding layer is also placed around the copper busbar to prevent electromagnetic interference from affecting the signal transmission of the battery management system (BMS).
Environmental adaptability testing is the final hurdle in verifying the reliability of the copper busbar. By simulating extreme conditions such as high temperature and humidity, salt spray corrosion, and mechanical vibration, the performance degradation of the copper busbar during long-term use is examined. For example, after continuous exposure to an environment of 85°C and 85% humidity for hundreds of hours, the insulation resistance of the copper busbar must still maintain more than 90% of its initial value to ensure that leakage or short circuits do not occur under harsh weather conditions.
From material selection and process control to structural design and environmental verification, the connection stability of the copper busbar in new energy vehicle battery packs is comprehensively guaranteed through multi-dimensional technical means. This systematic solution not only meets the high energy density requirements of current battery systems but also provides a reliable path for future power transmission with higher voltage and greater current.
