Aluminium-to-aluminium and copper-to-copper joints are widely used combinations of materials for the busbar joints (due to their high conductivity) for electric vehicles. Ultrasonic welding has emerged as a most promising solid-state joining process due to its ability to avoid intermetallic formation, less porosity formation, and larger weld area than fusion-type welding. The key parameters affecting an ultrasonic joint’s quality are clamp pressure, vibrational amplitude, weld time, and weld energy. In general, ultrasonic welding is done by varying either time or energy. Although USMW holds such suitability for the busbar joining process, very few studies have been conducted to determine the consistency of weld quality between these two modes. In this study, two types of joints of Al-Al and Cu-Cu were made under both time and energy modes while keeping the welding pressure and amplitude constant. Microstructural characterisations were carried out to understand the joining mechanism during both welding modes. Further, the mechanical behaviour of the joints (lap configuration) was investigated using the lap shear test. The lap shear strength for the busbar joints obtained under both modes unveiled high deviation in the strength for the sample welded under the time mode, while the samples welded with energy mode showed relatively consistent results. This study found that the energy mode was preferred for welding to reduce variation.