Application of Copper Wires in New Energy Vehicles

Copper wire serves as the core conductor of the electrical system in new energy vehicles. Benefiting from high electrical conductivity, good ductility, mature welding and crimping processes, excellent vibration resistance and stable contact performance, copper wire remains the mainstream solution for high-voltage power circuits and low-voltage signal circuits in vehicles. The consumption of copper in a pure electric vehicle is far higher than that of fuel vehicles. With the popularization of 800V high-voltage platforms, the market demand for high-quality copper wires keeps rising.

1. Main Application Scenarios

1. Vehicle High-Voltage Copper Wires (Power Main Cables with Orange Sheath) Applied to 400V/800V high-voltage DC platforms, capable of carrying hundreds of amperes of large current.

• High-power transmission cables connecting the battery pack with motor control unit (MCU), on-board charger (OBC), DC-DC converter and PTC heater;
• Power transmission wires inside fast-charging ports and charging guns; Common cross-sectional specifications: 10, 16, 25, 35, 50, 70, 95, 120 mm² large-section copper wires.

2. Low-Voltage Copper Wires (Vehicle Signal & Auxiliary Power Supply) Used in 12V/48V on-board systems for BMS, various sensors, vehicle lamps, cabin electrical appliances, automotive Ethernet and signal transmission of each controller.

• Conductors adopt fine tin-plated copper stranded wires, with mainstream specifications of 0.35~2.5 mm²;
• Features: Large quantity of harnesses, accounting for the largest proportion of vehicle wiring harnesses, and also the first field where “aluminum replacing copper” is piloted. However, high-speed signal and precision sensor circuits still adopt copper wires due to strict requirements for signal stability.

3. Copper Conductors for Battery Packs (Bus Connection) Besides conventional cables, flexible copper connectors, copper busbars and copper strip tabs belong to the copper conductor system, used for series-parallel connection of battery cells and high-current connection between modules. Materials are mostly T2 red copper, silver-plated or nickel-plated copper, which can sustain continuous heavy current and reduce circuit heating risks.
4. Copper Wires for Drive Motor Windings Hairpin flat enameled copper wire has become the mainstream solution for the stator windings of drive motors. It features high slot filling factor, which helps improve motor power density and lower temperature rise. Motor windings represent one of the largest copper consumption segments in new energy vehicles, and large-scale aluminum substitution cannot be realized in the short term.

2. Industry Material Selection Standards

1. Material: TU1/TU2 oxygen-free copper is preferred for high-voltage main wires, with copper purity ≥99.99%, low oxygen content and electrical conductivity ≥100% IACS to reduce heat generation under high-current working conditions. Conductors are tinned to prevent oxidation and improve the reliability of welding and crimping.
2. Structure: Multi-strand Class 6 flexible stranded conductors are adopted to adapt to continuous bumping and vibration during vehicle operation and avoid wire breakage. High-voltage cables are additionally equipped with braided copper shielding layers.
3. Environmental indicators: Able to withstand low temperature of -40℃ and long-term operating temperature of 125~150℃. With properties of oil resistance, hydrolysis resistance and UL94 V-0 flame retardancy. Full vehicle certification including thermal cycling, salt spray and vibration tests is required.

3. Industry Development Trends

1. High-voltage Platform Upgrade (from 800V to 1000V): The increase of platform voltage raises higher requirements on current-carrying capacity, temperature resistance and electromagnetic shielding performance of copper wires. Cable insulation layers are thickened and shielding structures are upgraded. Liquid-cooled copper cables are adopted in some ultra-fast charging scenarios.
2. Continuous Technological Upgrade of Copper Wires: Technologies such as ultra-fine stranding, ultra-thin insulation and lightweight copper plating are iterated continuously to reduce harness weight while retaining high reliability of copper.
3. Copper-aluminum Hybrid Wiring Becomes Mainstream Instead of Full Substitution: Copper wires are prioritized for scenarios with large current, high reliability and narrow installation space. Aluminum wires or copper-clad aluminum are used in low-voltage, long-distance and cost-sensitive parts. Connector terminals and contacts basically retain copper alloy solutions.
4. Rising Demand for Flat Copper Windings: The market of hairpin flat copper wires for electric drives grows rapidly, becoming the largest incremental segment of copper demand for new energy vehicles.

4. Industry Pain Points of Copper Wires

1. Cyclical fluctuations in copper prices directly squeeze the profit margin of harness manufacturers. China has a high external dependence on copper resources.
2. Copper has high density, resulting in heavy harness weight, which adversely affects vehicle cruising range and accelerates R&D of aluminum substitution technologies in the industry.
3. High-voltage copper wires have high technical barriers in production, shielding processing and vehicle assembly, and vehicle specification certification takes a long cycle.