In the process of the automotive industry's accelerated transformation towards electrification, the 48V system has emerged as a key technology for enhancing vehicle performance and optimizing energy efficiency. This system, with its unique advantages, has carried out a comprehensive technical reconstruction of automotive wiring harnesses, injecting strong impetus into the upgrading and replacement of automotive electrical architectures.

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Thread Diameter slimming Revolution

According to Ohm's Law (P=UI), when a 48V system outputs the same power, its operating current is only one fourth of that of a 12V system. Take a 3kW integrated generator as an example. The 12V system needs to carry a current of 250A, and the cross-sectional area of the wire is approximately 35mm². The 48V system only requires 62.5A and a cross-sectional area of 10mm². The actual test on the Volkswagen MQB platform shows that after using a 48V wire harness with a 4mm² cross-section, the weight of a single wire is reduced by 60%, and the bending radius is optimized from 8D of the 12V wire harness to 5D (D is the wire diameter). This not only significantly reduces the weight of the wiring harness but also enables it to adapt to the more complex wiring paths of the hybrid power system, enhancing the flexibility of the spatial layout. The Mercedes-Benz S-Class Hybrid model has increased the space utilization rate of the engine compartment by 19% through optimizing the wiring harness layout, thus freeing up more space for the rational placement of other components.

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Heat loss has dropped sharply

According to Joule's Law (Q=I²Rt), a third-party laboratory's tests under simulated urban conditions show that when a 48V system transmits 20kW of energy, the total heat loss of the wiring harness is only 1/16 of that of a 12V system. When the ambient temperature is 40℃, the surface temperature of the 12V system wiring harness reaches 82℃, while that of the 48V system remains stable within the range of 58-60 ℃. The lower heat loss has expanded the range of insulating material options. Continental has adopted modified TPE materials to replace traditional PVC. Although the temperature resistance grade of the modified TPE material has been reduced to 90℃, its flexibility has increased by 35%, which is more in wire with the operation requirements of automatic wiring robots and provides convenience for the automated production of wire harnesses.

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Electrical safety and protection upgrade

In terms of electrical safety, the 48V system performs exceptionally well. Its short-circuit protection response time has been shortened from 100ms in a 12V system to 20ms, which can quickly cut off fault currents and reduce safety risks. The newly added IP6K9K waterproof standard requires connectors to pass an 8-hour high-pressure steam jet test. The 48V battery wiring harness of Tesla Model 3 uses laser welding sealing technology to meet this standard, effectively preventing water vapor from entering. The third-generation high-voltage interlock system developed by Aptiv achieves a 10ms-level fault response through PWM signal detection, which is five times faster than traditional solutions, greatly enhancing the timeliness of system fault monitoring and handling.

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Electromagnetic shielding and wiring optimization

The 48V wiring harness of the BMW 5 Series Hybrid model adopts a sandwich shielding structure of 0.1mm aluminum foil + 92% coverage copper braided mesh + nano-graphite coating, with a shielding efficiency of 72dB at the 1MHz frequency point. Among them, the woven net is formed by a 32-spindle high-speed weaving machine at a 28° bevel Angle. Compared with the traditional 45° weaving method, the high-frequency shielding performance is improved by 15%. The grounding points of the wire harness adopt a star topology structure, and the potential difference between each grounding point is controlled within 50mV, effectively suppressing common-mode interference. The Volvo SPA2 platform specification requires that the 48V positive and negative pole wires be arranged as twisted-pair wires (twist pitch ≤50mm), with a horizontal distance of ≥150mm from the ADAS camera. When crossing with the 12V wire harness, a 90° vertical cross should be adopted and ferrite magnetic rings should be installed at the intersection points. A Japanese brand's actual test shows that this layout reduces the CAN bus bit error rate from 10⁻⁶ to 10⁻⁹, significantly enhancing the stability of signal transmission.

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Cost control and material innovation

Industry data shows that the proportion of connectors in the cost structure of 48V wiring harnesses has dropped from 45% in 2018 to 28% in 2023. This is attributed to the VHB series of standardized connectors launched by TE Connectivity, whose mold reuse rate reaches 80%, effectively reducing manufacturing costs. The cost of shielding materials has also decreased significantly. The composite shielding tape developed by Lenny Cable has reduced copper usage by 40%, and 3M's conductive tape solution has further reduced the total weight by 15%. It is expected that by 2026, automated production lines featuring robot laser wire stripping and visual inspection will reduce the proportion of labor costs from 25% to 8%. In terms of material innovation, BASF's Ultramid® Advanced N series materials, through 40% glass fiber + 5% ceramic composite filling, achieve dimensional stability of ±0.05mm for connectors under operating conditions ranging from -40 ° C to 150 ° C. Its CTI value of 600V means it can withstand higher working voltages in polluted environments, providing strong support for the redundant design of 48V systems. Continental is testing a liquid metal shielding coating that can further enhance the high-frequency EMI performance of wiring harnesses by 20dB, continuously driving the advancement of 48V wiring harness technology. ​

The technical reconfiguration of the wiring harness in the automotive 48V system is a comprehensive and profound transformation. Through optimization and upgrading in multiple aspects such as wire diameter, heat loss, electrical safety, electromagnetic shielding, cost control and materials, not only has the performance and reliability of the wiring harness been enhanced, but also a solid foundation has been laid for the intelligent and lightweight development of automobiles, effectively promoting the automotive industry to make great strides towards a more efficient, environmentally friendly and intelligent direction.

[Note: The above is merely my personal opinion. Discussions on wiring harness knowledge are welcome.]