High-voltage wiring harness and production process optimization solution for pure electric vehicles

This article briefly introduces the high-voltage wiring harness and production process of pure electric vehicles, and makes a detailed analysis of the cost structure of the high-voltage wiring harness and the material cost structure. It studies the cost reduction methods of high-voltage system architecture optimization, high-voltage wiring harness layout optimization, high-voltage wiring harness material optimization, platformization and standardized design, which is of great significance to the cost optimization of high-voltage wiring harness.

1 Introduction

At present, the competition in the domestic new energy vehicle market is becoming increasingly fierce. With the price reduction of domestic Tesla and the entry of Volkswagen's electric models, the subsequent competition will become more intense. Only by relying on high-quality, high-value products and leading technologies can automobile companies occupy a place in the fierce new energy vehicle market. While major automobile companies are constantly innovating in technology, they are also focusing on optimizing component costs, improving product strength and enhancing corporate competitiveness. High-voltage wire harnesses are high-value components in pure electric vehicles and are also the main components for cost optimization.

2 High voltage wiring harness introduction and production process

The high-voltage wiring harness connects the various components of the high-voltage system. As a medium for high-voltage power transmission, it is the main carrier of power output in electric vehicles and is mainly used to transmit electrical energy and shield external signal interference. The high-voltage wiring harness has the characteristics of high voltage, large current, high protection level and anti-electromagnetic interference. It is the neural network of the high-voltage system of pure electric vehicles and a key component for the performance and safety of the whole vehicle. The high-voltage wiring harness of pure electric vehicles is generally divided into power battery high-voltage wiring harness, motor controller high-voltage wiring harness, fast charging socket wiring harness, slow charging socket wiring harness, air conditioning system wiring harness and charging high-voltage wiring harness. Among them, the charging high-voltage wiring harness refers to the wiring harness connecting the high-voltage distribution box to the on-board charger, air conditioning compressor and power battery pack heater.

High-voltage wire harnesses are mainly composed of high-voltage connectors, high-voltage cables, coverings (tapes, heat shrink tubes, corrugated tubes, wear-resistant self-rolling tubes, etc.), protective plates, etc. The production process of high-voltage wire harnesses mainly includes wire cutting, accessory pre-installation, terminal crimping/ultrasonic welding, shield crimping, wire harness assembly and electrical inspection.

3. Analysis of high voltage wiring harness cost structure

The cost of high-voltage wire harnesses is composed of material costs, processing fees, packaging and transportation fees, and profit and management fees. The material cost of high-voltage wire harnesses is mainly determined by the wire harness technology solution, among which the processing fee includes labor costs, power costs, equipment depreciation costs, and low-value consumables. The following is a high-voltage wire harness cost composition ratio diagram (see Figure 1) and a high-voltage wire harness material cost composition ratio diagram (see Figure 2) for a certain model. The material cost of high-voltage wire harnesses accounts for about 73.8% of the total cost of the wire harness. It is necessary to continuously reduce the cost of high-voltage wire harnesses through methods such as optimizing design and optimizing production processes.

Figure 1: Cost composition of high-voltage wiring harnesses

Figure 2: High-voltage wiring harness material cost composition

4. Study on cost optimization of high voltage wiring harness

There are three main methods for enterprises in the automotive industry to reduce costs: scale, supplier collaboration, and technology. Among them, technology is the most effective and sustainable method to reduce costs. At present, there are three main methods for reducing costs through technology: cost benchmarking, management technology, and technical means.

Generally speaking, the technical means method includes reducing redundant functions, increasing the localization rate, and standardizing specifications. In the cost reduction activities of high-voltage wiring harnesses for pure electric vehicles, this study mainly uses the technical means method to optimize the cost of high-voltage wiring harnesses from the following aspects.

4.1 High-voltage system architecture optimization

In pure electric vehicles, high-voltage components include power batteries, three-in-one (motor controller + drive motor + differential), PDU (high-voltage distribution box), ECP (electric compressor), two-in-one (IPS=OBC+DC-DC), HVH (battery heating), PTC (passenger heating), slow charging seat (AC Inlet), fast charging seat (DC Inlet) and high-voltage wiring harness, etc. These components constitute the high-voltage system of the whole vehicle. If the high-voltage system architecture of pure electric vehicles is well optimized, the number of connectors used and redundant high-voltage wiring harnesses can be greatly reduced. Taking the optimization of the high-voltage system architecture of a certain project as an example, before the optimization, the PDU in the high-voltage wiring harness system architecture only exists as a power distribution function module, and there is no module related to the functional performance of the whole vehicle, as shown in Figure 3.

Figure 3 High-voltage system architecture before optimization

The independence of PDU increases the number of transfers in the high-voltage wiring harness system. The functions of HVH and PTC are similar, which increases the number of high-voltage wiring harness loops. The fast and slow charging sockets are arranged on the left and right rear side panels, which are too far away from the electrical appliance interface (the battery fast charging interface is in the front, and the charger slow charging interface is in the front compartment), making the high-voltage wiring harness longer. After research and analysis, the electrical components that realize the functions are copper bars that are only used for connection functions and fuses for power protection functions, and the integration with other electrical appliances is not difficult. The integration of PDU and IPU can cancel a high-voltage distribution box assembly, and at the same time save a set of motor controller wiring harnesses (about 1.5m of 50mm2 wires and two pairs of φ8mm terminal connectors), which can bring obvious cost-saving benefits. HVH and PTC have similar functions. The two functions are combined, and the high-voltage wiring harness can reduce one loop (about 1.5m of 3mm2 wires and two pairs of 2.8mm wide terminal connectors). The optimized high-voltage system architecture is shown in Figure 4.

Figure 4 Optimized high-voltage system architecture

Through this high-voltage system architecture optimization, four high-voltage connectors and two high-voltage wire harnesses were reduced, and the cost of the high-voltage wire harness can be reduced by approximately RMB 730.

4.2 High-voltage wiring harness layout optimization

The layout of high-voltage wiring harnesses needs to be continuously optimized according to the vehicle model. After optimization, the use of high-voltage cables can be reduced, further reducing costs. Taking the optimization of the layout of the fast and slow charging ports of a certain vehicle model as an example, before optimization, the fast and slow charging ports were arranged on the left and right rear side panels, and the length of the fast and slow charging harnesses was too long, of which the slow charging harness length was about 4.5m and the fast charging harness length was about 4m, resulting in high costs for the fast and slow charging high-voltage harnesses. After optimization, the charging ports are arranged on the left and right fenders, close to the charger and battery pack, to reduce the length of the high-voltage harness. The layout diagrams before and after optimization are shown in Figures 5 and 6. This optimization of the high-voltage harness layout can reduce costs by about 260 yuan.

Figure 5: Layout of fast and slow charging ports before optimization

Figure 6 Optimized layout of fast and slow charging ports

4.3 High-voltage wiring harness material optimization

In the cost structure of high-voltage wiring harnesses, material costs account for the highest proportion. Based on an analysis of the current status, the current optimization directions for high-voltage wiring harness materials are mainly the integrated design of charging sockets, localization of high-voltage connectors, optimization of high-voltage cable diameters, and one-to-many optional optimization of materials.

4.3.1 Optimization of integrated design of charging socket

Before optimization, the charging socket was a split design with high cost. The split charging socket before optimization is shown in Figure 7, including a fast charging socket and a slow charging socket. The charging socket is developed and designed according to the platform solution, and the main structure of the charging socket of all projects is solidified to minimize the development cost. The optimized integrated charging socket is shown in Figure 8. This optimization can reduce one set of flange molds, thereby reducing the cost of the high-voltage wiring harness assembly by about 8 yuan.

Figure 7 Split charging socket before optimization

Figure 8 Optimized integrated charging socket