As the medium for high voltage power transmission, the high voltage harness connects the components of the high voltage system, carries electrical energy and shields against external interference, making it the main carrier of power output in a new energy vehicle. It is characterised by high voltage, high current, a high ingress protection rating and resistance to electromagnetic interference, and it is the nervous system of the high voltage system and a key component for vehicle performance and safety. High voltage harnesses and connectors are therefore a critical part of the power transmission system, and their design and selection affect vehicle performance and safety.

1. Why design and selection matter

1.1 The foundation of efficient power transmission. In a new energy vehicle the battery is the source of power, but its stored energy is limited. Reducing losses during transmission means using the limited battery energy more effectively and extending range. This requires conductors with excellent conductivity and an optimised layout of conductor cross sections to reduce resistance and heat loss. Power demand fluctuates with driving conditions, and good harness design handles these fluctuations smoothly, ensuring a continuous and stable supply to the motor and other consumers.

1.2 Safeguarding safety. The high voltage harness has good insulation to prevent current leakage. Insulation materials are selected rigorously so that they withstand the vehicle operating voltage, usually above 400 V, over the long term. Dielectric design is critical to ensure that the harness does not fail under excessive voltage in extreme conditions, protecting the vehicle and its occupants.

1.3 Improving system reliability. Careful planning of harness routing and fixing reduces vibration and abrasion during operation and lowers the risk of damage. Good layout keeps performance stable in complex environments and improves system reliability. Conductors made from materials with high conductivity and heat resistance significantly extend harness life, resist harsh operating conditions and reduce failures caused by material ageing.

1.4 Driving technical progress. As new energy vehicle technology develops, requirements for high voltage harnesses and connectors keep rising. Research into harness design and connector selection meets current market needs, drives technical innovation and promotes the development of the whole industry in a virtuous cycle.

1.5 Cost optimisation. Besides performance and safety, cost is a factor every manufacturer must consider. Good harness design and connector selection optimise cost while maintaining performance and safety, improving market competitiveness and supporting sustainable development.

2. High voltage harness design

2.1 Design approach

(1) Design goals. The design meets the requirements of new energy vehicles for high efficiency and high safety in the high voltage harness, optimising layout, selecting suitable materials and using advanced manufacturing processes to achieve a lightweight harness with efficient transmission.

(2) Harness layout. Plan the high voltage harness route according to the chassis structure, avoiding runs that are too long or too short and reducing vibration and abrasion during operation. Use reliable fixing with dedicated clips and brackets so that the harness does not shake loose while driving, and add protective sleeving in areas prone to wear or environmental exposure to prevent damage.

(3) Material selection. Choose conductor materials with high conductivity, heat resistance and corrosion resistance, such as high temperature superconducting materials or special alloy conductors, so that performance stays stable in harsh conditions of high temperature and humidity. Use high performance insulation such as polyimide (PI) or polytetrafluoroethylene (PTFE) for good electrical insulation. Choose connectors in high strength, high conductivity metals such as copper alloy or stainless steel so that contact problems do not arise over long service.

(4) Manufacturing process. Use automated production lines for high voltage harnesses to raise efficiency and ensure quality. Use precision crimping equipment to ensure reliable conductor to connector connection and reduce contact resistance and temperature rise. Carry out strict quality inspection in production, including conductor resistance testing and connector insertion force testing, so that harness performance meets the design requirements.

(5) Safety protection. Fit overcurrent protection such as fuses or circuit breakers in the high voltage harness to prevent damage from excessive current. Ensure effective separation between the high voltage harness and low voltage and control harnesses to avoid electromagnetic interference and potential safety risks. Design the grounding system properly so that the high voltage harness is reliably earthed, reducing electromagnetic interference and the risk of static accumulation.

2.2 Layout principles

High voltage harness layout should follow the basic principles of safety, reliability, economy and maintainability. Safety requires routing away from heat sources and moving parts to prevent damage and fire. Reliability requires stable connections that resist vibration, temperature, humidity and other environmental factors. Economy requires minimising harness length and material use while meeting performance requirements. Maintainability requires neat routing and clear marking so that inspection and replacement are easy.

2.3 Materials and manufacturing process

(1) Conductor materials. High voltage harnesses in new energy vehicles mainly use high purity copper or aluminium conductors with good conductivity to meet high current and high voltage transmission needs. Copper is widely used for its conductivity and mechanical strength, while aluminium offers advantages in lightness and cost in some applications. To ensure safety the conductor is covered with insulation, commonly cross-linked polyethylene (XLPE), polyvinyl chloride (PVC) or ethylene propylene rubber (EPR); XLPE is favoured in new energy vehicles for its electrical performance and heat resistance.

(2) Shielding materials. To prevent electromagnetic interference (EMI) affecting other electronic systems, high voltage harnesses use shielding materials that absorb electromagnetic waves and reduce interference, commonly metal braid, aluminium foil and conductive cloth.

(3) Sheath materials. The sheath protects the harness from the external environment and must offer weather resistance, abrasion resistance, oil resistance and flame retardance; common sheath materials include PVC, thermoplastic elastomer (TPE) and nylon.

Conductor manufacture involves drawing, annealing and stranding: raw metal is drawn to the required wire diameter, annealed to improve flexibility, and several strands are stranded together to increase mechanical strength. Insulation is applied by extruding insulating material evenly over the conductor and cooling it to form a solid insulating layer. Shielding manufacture wraps metal braid or aluminium foil tightly around the insulation, ensuring close contact with the conductor to reduce electromagnetic interference effectively. Both ends of the high voltage harness carry connectors for connection to other vehicle electrical systems; connector manufacture requires precision machining and injection moulding to ensure accuracy. During assembly the conductor must make close contact with the connector to reduce contact resistance and improve conductivity.

3. Connector selection

3.1 Performance requirements

(1) Electrical performance. The rated voltage of the connector must meet the vehicle voltage requirement. Given the high voltage system, the rated voltage should be above 200 V to ensure safe and stable operation in a high voltage environment. Insulation resistance is an important indicator, ensuring that no leakage or short circuit occurs at high voltage and meeting relevant standards, for example 100 MΩ. Dielectric withstand performance should be above 1,000 V to ensure safe operation in the high voltage system.

(2) Mechanical performance. Insertion and withdrawal force reflects ease of use: it must be within a specified range, easy to operate but not too loose, and is usually required to be no more than 100 N. Mechanical life is the number of insertion and withdrawal cycles the connector can perform normally while remaining stable and reliable over long use, generally required to be more than 50 cycles. Because a vehicle vibrates while driving, connectors must resist vibration well, with no effect on electrical or mechanical performance at specified frequencies and amplitudes.

(3) Temperature adaptability. Connectors must work normally over a wide temperature range, from -40℃ to 125℃, with no effect on electrical or mechanical performance, as shown in Table 1.

(4) Corrosion resistance. Material selection determines corrosion resistance. The housing should preferably use a metal with excellent corrosion resistance such as aluminium or zinc alloy, with a blasted surface finish. Contact parts should use pure copper with gold, silver or nickel plating to improve conductivity while meeting corrosion requirements. The connector should be well sealed against moisture, dust and other harmful substances to avoid corrosion, with a well designed sealing structure that keeps its effect in harsh environments. A corrosion resistant coating on the surface can reinforce protection and ensure the connector mates tightly without loosening, and a special sealed wrap can protect the joint from moisture and corrosive substances. Regular maintenance and inspection are an important measure for long term corrosion resistance.

3.2 Types and characteristics

(1) LV standard connectors. LV standard connectors are the most widely used in the Chinese market, with relatively mature process standards. They suit many electrical connection needs, are highly versatile and are widely used for key components such as battery packs and motor controllers in new energy vehicles.

(2) USCAR standard connectors. USCAR standard connectors are international standard connectors with high compatibility and reliability. Their design meets the strict requirements of the automotive industry, ensuring stable operation in harsh environments, and they are mainly used in international brand new energy vehicles to meet global market needs.

(3) Japanese standard connectors. Japanese standard connectors are designed to Japanese standards, emphasising refinement and high performance, with small size and excellent electrical performance.

Because of the high voltage system in new energy vehicles, connectors must withstand high voltage and high current surges to ensure stable power transmission. Design must focus on the choice of insulating materials to prevent leakage and short circuits, maintain stable electrical performance at high temperatures, and be easy to install and remove so that maintenance and replacement can be done quickly.

4. Conclusion

High voltage harness design and connector selection are key factors in ensuring the performance and safety of new energy vehicles. This article has examined both in depth, providing a reliable and efficient solution for new energy vehicle electrical systems.