4. Busbars for e-mobility: State-of-the-Art Review and a New Joining by Forming Technology

The changes in the automotive market and their effects on industry are nowadays hot topics in metal forming seminars and conferences around the world. The rise in the number of electric vehicles will inevitably lead to a decrease in the demand of components for combustion engines and power drive trains. Typical forming components such as pistons, connecting rods, valves, camshafts, crankshafts, multi-speed gear boxes and others that exist in diesel or petrol vehicles, will no longer be required. However, the lightweight construction requirements for the body-in-white of electric vehicles, the production of components for asynchronous motors and the fabrication of battery components, namely busbars, are bringing new challenges and opportunities for the metal forming industry. This chapter is focused on busbars, which are metallic strips or sheets that are utilized to distribute electric power to multiple equipment such as the electric motor, the electric power steering unit, and the AC/DC converters. In particular, the chapter addresses the challenge of replacing copper busbars by hybrid busbars made from copper and aluminium, due to the expected savings in weight and cost. For this purpose, the authors discuss the challenge of connecting copper to aluminium in hybrid busbars by means of existing joining technologies and introduce a new joining by forming process aimed at connecting hybrid busbars at room temperature without giving rise to material protrusions above and below the sheet surfaces. The effectiveness of the new process is compared against fastening by measuring the electric resistivities in both types of hybrid busbar joints. Finite element analysis gives support to the presentation and proves to be suitable for the electro-thermo-mechanical analysis of busbar connections.