Copper prices and vehicle weight targets have pushed the new energy industry to take aluminum conductors seriously for high-voltage harnesses. Aluminum conducts about 61% as well as copper by volume but weighs less than a third as much per volume — a compelling trade for multi-meter battery cabling. The engineering question is not whether aluminum works, but where its termination and reliability requirements fit your program. This article summarizes the practical state of the art.
The Weight and Cost Case
A 2-meter 95 mm² battery main cable in copper weighs roughly 3.4 kg; the aluminum equivalent conductor weighs about 1.1 kg even after upsizing the cross-section to match resistance. For vehicles carrying several such runs — pack to PDU, pack to motor inverter, DC fast-charge cabling — the savings reach several kilograms. Cost per meter is also lower and less volatile, which matters at automotive volumes.
The Termination Challenge
Aluminum's difficulties are all at the ends, not in the middle of the cable:
- Oxide layer: aluminum forms a tough oxide film instantly; terminations must penetrate or break through it to make metal-to-metal contact.
- Creep (cold flow): aluminum slowly deforms under clamping pressure, loosening bolted joints over time. This is why compression-type lugs with Belleville washers and torque monitoring are standard practice.
- Galvanic corrosion: aluminum touching copper in the presence of electrolyte corrodes the aluminum. Transitions use bimetallic terminals (aluminum barrel, copper palm) or sealed interfaces.
- Ultrasonic welding: where harnesses join aluminum conductors to busbars, ultrasonic welding removes the oxide and produces a stable solid-state joint — the preferred process in battery interconnect manufacturing.
Our article on ultrasonic welding in wire harness manufacturing explains why the process dominates this field.
Where Aluminum Wins — and Where It Does Not
Aluminum fits best in long, straight, large-cross-section runs with bolted or welded terminations: battery main circuits, inverter feeds and charging infrastructure cabling. It fits poorly where harnesses must flex repeatedly in small radii (fine-stranded copper still wins), where connectors use crimp contacts designed for copper-class strand packs, or where serviceability in the field involves repeated disconnection of small terminals.
Copper-Clad Aluminum as a Middle Path
CCA (copper-clad aluminum) conductors combine an aluminum core with a copper skin, easing termination and corrosion concerns at a weight saving between the two metals. They are established in signal and RF applications and increasingly evaluated for light power circuits, but high-current EV main circuits still favor either pure copper or properly engineered pure-aluminum terminations.
Designing an Aluminum High-Voltage Harness
The decision needs to happen at the system level: conductor upsizing affects channel and gland sizes, termination processes change the manufacturing plan, and service documentation must state torque values. Kaweei manufactures high-voltage harnesses for new energy applications in copper and, for suitable programs, aluminum constructions with engineered terminations. To discuss whether aluminum fits your platform, contact our engineering team — and see our guide to high-voltage wiring harnesses for the overall design framework.