To enhance electric vehicle (EV) performance, researchers at SINTEF (The Foundation for Industrial and Technical Research) and NTNU (Norwegian University of Science and Technology) have unveiled a promising approach to reduce the weight of EV wiring. The innovation centers around replacing portions of traditional copper wiring with lighter aluminium, while overcoming the challenges associated with joining these dissimilar metals.

The weight of EVs plays a crucial role in their energy consumption as it directly impacts range and efficiency. While copper is the industry standard for electrical conductors due to its excellent conductivity, availability, and malleability; its heavy weight contributes to the overall burden in larger vehicles like buses. Researchers estimate that copper wiring can weigh between 83 to 369 kg (183-814 lbs) in passenger cars and buses, respectively.

To address this, the Norwegian team explored the use of aluminium, a metal with comparable conductivity and malleability but significantly lower density—approximately one-third that of copper. However, the challenge lies in effectively joining copper and aluminium without compromising conductivity. Traditional high-temperature welding methods often result in the formation of brittle intermetallic compounds, which degrade electrical performance.

The breakthrough came with the application of a patented technique known as Hybrid Metal Extrusion & Bonding (HYB), developed at NTNU. This cold-welding process utilizes mechanical pressure and friction to create thin, stable intermetallic bonds at the copper-aluminium interfaces, minimizing the formation of detrimental compounds. This method allows for the creation of hybrid conductors with distinct segments, each tailored to specific roles within the EV’s electrical system.

The implications of this research are particularly significant for Norway, a global leader in EV adoption, with approximately 89% of new car sales in 2024 being fully electric. Reducing the weight of EV wiring translates directly to extended range, a critical factor for consumer adoption. Moreover, it opens up new possibilities for electrifying commercial transportation, such as buses and trucks, by improving their range and efficiency.

"The HYB method creates thin and slow-growing intermetallic bonds at the interfaces of copper and aluminium using mechanical pressure and friction," explains Jørgen A. Sørhaug from SINTEF. "This is better because the electrical and mechanical properties of the hybrid conductor are less prone to change."

Electron microscopy techniques were employed to meticulously examine the interfaces and validate the properties of the hybrid conductors. Early results indicate that the HYB technique produces stronger bonds between copper and aluminium compared to conventional welding methods.