Thermal-electrical analysis of a novel interconnection for hybrid busbars in electric vehicle batteries

Reliable and efficient busbar connections are critical for electric vehicle battery performance, yet conventional joining methods struggle with joining dissimilar materials such as copper and aluminum. This paper investigates a novel solution for joining hybrid copper-aluminum busbars using a technique called hole hemming, which eliminates the need for heating or additional elements. The focus is placed on the thermal-electrical performance of hole-hemming joints. Two configurations are studied: joints with and without branches. Numerical models analyse how sheet thickness affects temperature, electric current density, electric potential, and resistance, including models with cantered holes to study hole inclusion effects. Experimental tests are conducted on material strips and unit cells to assess electrical resistance changes with temperature and the effect of Joule heating on joint configurations. Compression using a hydraulic press is applied to improve contact, leading to significant electrical resistance improvements (78 % reduction for branched joints and 36 % for branchless ones). Mechanical shear tests before and after compression show a peak shear load of 4.54 kN and 13.84 mm displacement for branched joints, with slightly lower values for branchless joints. Despite a minor decrease in mechanical performance after compression, the improved thermal-electrical performance of the joints outweighs this. The findings highlight the promising potential of hole-hemmed joints for enhancing hybrid busbar connections.