Cost Optimization of High-Voltage Wire Harness of Pure Electric Vehicle

At present, the competition in the domestic new energy vehicle market is becoming more and more fierce. With the price reduction of domestic Tesla and the participation of Volkswagen's electric vehicles, the follow-up competition will become more intense. Only by virtue of high-quality, high-value products and leading technology, enterprises can occupy a place in the fierce new energy vehicle market. While constantly innovating in technology, major car companies are also focusing on cost optimization of spare parts, improving product strength and enterprise competitiveness. High-voltage wire harness is a high-value component in pure electric vehicle, and it is also the main component for cost optimization.

High-voltage wiring harness connects the components of high-voltage system, serves as the medium of high-voltage power transmission, and is the main carrier of power output on electric vehicles, which is mainly used to transmit electric energy and shield external signal interference. High-voltage wiring harness has the characteristics of high voltage, high current, high protection level and anti-electromagnetic interference. It is the neural network of high-voltage system of pure electric vehicle, and is the key component of vehicle performance and safety. Generally, pure electric vehicle high-voltage harness is divided into power battery high-voltage harness, motor controller high-voltage harness, fast charging socket harness, slow charging socket harness, air-conditioning system harness and charging high-voltage harness, among which charging high-voltage harness refers to the harness connecting high-voltage distribution box to on-board charger, air-conditioning compressor and power battery pack heater.

High-voltage wire harness is mainly composed of high-voltage connector, high-voltage cable, coating (adhesive tape, heat shrinkable tube, corrugated tube, wear-resistant self-rolling tube, etc.), protective plate, etc. The production process of high-voltage wire harness mainly includes wire cutting, pre-assembly of accessories, terminal crimping/ultrasonic welding, shielding crimping, assembly of wire harness and electrical inspection.

The cost of high-voltage wire harness consists of material cost, processing cost, packaging and transportation cost and management cost. The material cost of high-voltage wire harness is mainly determined by the technical scheme of wire harness, and the processing cost includes labor cost, power cost, equipment depreciation cost and low-value consumables.

There are three main ways to reduce the cost of automobile enterprises: scale, supplier cooperation and technology, among which technology is the most effective and sustainable way to reduce the cost. At present, there are three methods to reduce the cost of technology: cost benchmarking, management technology and technical means.

In general, technical means include reducing redundant functions, improving localization rate, and standardizing specifications. In the activity of reducing the cost of high-voltage wiring harness of pure electric vehicle, this research mainly uses technical means to optimize the cost of high-voltage wiring harness from the following aspects.

In pure electric vehicles, the high-voltage components include power battery, three-in-one (motor controller+driving motor+differential), PDU (high-voltage distribution box), ECP (electric compressor), two-in-one (IPS=OBC+DC-DC), HVH (battery heating), PTC (occupant heating), slow seat charging (ACInlet) and fast seat charging. The high-voltage system architecture of pure electric vehicles is well optimized, which can greatly reduce the number of connectors and redundant high-voltage wiring harnesses. Taking the high-voltage system architecture optimization of a project as an example, before the optimization, the PDU in the high-voltage wiring harness system architecture only existed as a power distribution function module, and there were no modules related to vehicle functions and performance.

The independence of PDU increases the number of switches in the high-voltage harness system. The two functions of HV and PTC are similar, which increases the number of high-voltage harness circuits. The fast and slow charging sockets are arranged on the left and right rear side walls, which are too far away from the electrical interface (the fast charging interface of the battery is in the front, and the slow charging interface of the charger is in the front cabin), so that the length of the high-voltage harness is too long. After research and analysis, the functional electrical components are copper bars and fuses with power protection functions, so it is difficult to integrate with other electrical appliances. The integration of PDU with IPU can eliminate a high-voltage distribution box assembly, and at the same time, it can save a set of motor controller wiring harness (about 1.5m 50mm² conductor and two pairs of φ8mm terminal connectors), which can bring obvious cost reduction benefits. HV and PTC have similar functions. When these two functions are combined, the high-voltage wiring harness can reduce one loop (about 1.5m 3mm² conductor and two pairs of 2.8mm terminal connectors).

Through the optimization of the high-voltage system architecture, four high-voltage connectors and two high-voltage wiring harnesses are reduced, and the cost of high-voltage wiring harnesses can be reduced by about 730 yuan.

The layout of high-voltage wiring harness needs to be continuously optimized according to vehicle types. After optimization, the use of high-voltage cables can be reduced, and the cost can be further reduced. Taking the layout optimization of the fast and slow charging ports of a vehicle as an example, before optimization, the fast and slow charging ports are all arranged on the left and right side walls, and the length of the fast and slow charging harness is too long, of which the length of the slow charging harness is about 4.5m and that of the fast charging harness is about 4m, resulting in the high cost of the fast and slow charging high-voltage harness. After optimization, the charging ports are arranged at the left and right fenders, close to the charger and battery pack, so as to reduce the length of the high-voltage harness.

Among the components of high-voltage wiring harness cost, the material cost accounts for the highest proportion. Based on the analysis of the current situation, the material optimization direction of high-voltage wiring harness at present mainly includes integrated design of charging socket, localization of high-voltage connector, optimization of wire diameter of high-voltage cable and one-to-many optional optimization of materials.

Before optimization, the charging socket is designed in a split type, which has high cost and includes a fast charging socket and a slow charging socket. Through the development and design of charging sockets according to the platform scheme, the main structures of charging sockets of all projects are solidified to minimize the development cost. Through this optimization, a set of flange dies can be reduced, and the cost of high-voltage wire harness assembly can be reduced by about 8 yuan.

In recent years, the high-voltage connector industry has developed rapidly, and a number of excellent domestic high-voltage connector brand suppliers have emerged. Before optimization, foreign brands such as TE were mainly used for high-voltage connectors, which were continuously optimized through localization of high-voltage connectors, and replaced by domestic brands such as Luxshare and Ebusbar, which was of great significance to the cost reduction of high-voltage connectors.

Through the interpretation of regulations, benchmarking and statistics of cloud big data and other measures, the wire diameter of high-voltage cable is optimized. For the specific high-voltage cable, it can often be tailored by optimizing the cross section, temperature requirements, flexibility and shielding effect, so as to avoid excessive size and components. Take the fast charging high-voltage cable as an example, the cable diameter before optimization is 70mm², and the cable diameter after optimization is 50mm², which can meet the actual charging requirements.

One-to-many high-voltage wire harness materials can fully mobilize the enthusiasm of tier1 suppliers and make use of tier1 suppliers' own supply chain advantages to select the best cost scheme for supply. Take the high-voltage cable with high material cost as an example. At present, the main specifications of high-voltage cable are developed according to the high-voltage cable standard according to the one-to-many idea. Each specification wiring harness factory has multiple specifications to choose from, and the specific application of conductors in each circuit needs to be confirmed according to the actual load of the whole vehicle. Through continuous optimization design, many materials can be one-to-many optional at present.

Platform and standardization design from the aspects of the principle and raw materials of the whole vehicle harness can greatly shorten the development cycle of the whole vehicle harness design stage, reduce repeated verification tests and reduce the cost of the harness. Through the constant platformization and standardization of wire harness materials, the types of materials are reduced, and increasing the number of single materials can play a scale effect, which is of great significance to material cost reduction. After research and analysis, the material cost of high-voltage wiring harness can be greatly reduced through the platformization and standardization scheme of secondary materials (connectors, cables, accessories, etc.). The following is a platformization example of high-voltage plug-in. Under the condition of meeting the same electrical performance, the opening size of the aluminum alloy panel of battery pack can simultaneously install board-end connectors of different brands (TE, Luxshare).

High-voltage wire harness of pure electric vehicle has the characteristics of high voltage, high current and large wire diameter, and it faces challenges such as wiring, safety, shielding, weight and cost. As a high-value pure electric vehicle component, the high-voltage wiring harness can contribute to the cost reduction of the whole vehicle by studying the continuous cost optimization. Cost reduction is a continuous optimization activity, which needs to be continuously optimized in the follow-up, so as to minimize the cost of the whole vehicle and provide customers with more competitive products.