How electric vehicles impact cable harness design
A little-known fact in automotive electrics and electronics is that the wiring harness in the vehicle is one of the heaviest and most expensive individual parts of a car (after the engine and transmission). In addition, the vast range of variants of today’s vehicle models requires a tailor-made cable system for almost every possible configuration. Therefore, the cabling is largely manufactured by hand which makes it rather expensive.
The changes in vehicle electronics announced by the automotive industry will also result in massive changes in cabling: Introduction of a more centralized computer architecture with powerful domain computers instead of dozens of distributed ECUs; increased use of sensors with correspondingly higher data volumes within the vehicle and between the vehicle and the outside world, as well as the electrification of the drive train. It is precisely the latter factor that will significantly increase the amount of cabling in cars, explained Udo Hornfeck, Head of Research and Development at Leoni. The reason: electric vehicles require additional expensive high-voltage lines for AC-DC charging, high-voltage batteries and, traction as well as special wiring for the high-voltage battery and the battery management system. All these additional cables make the car more expensive. The fact that in return the combustion engine and thus the related wiring are omitted, does not make up for the price difference, the Leoni executive said.
Hornfeck explained that in addition to electrifying the drive system, driving automation and extended functionality in the comfort and infotainment areas would also contribute to rising prices. The reduction of the ECU number by the centralization of the computing resources, in contrast, will lead to less cable expenditure and therefore will have a price-reducing effect. The devices for automating driving have a relatively large share in this – for a car to automatically recognize the environment and adjust its driving strategy accordingly, significantly more sensors are required than in “normal” cars; in addition, data and power supply must be redundant, which also means more cabling. Some comfort functions – for example in the area of body control – have to be designed for high power peaks – this requires higher cable cross-sections and thus makes cabling more expensive, the R&D said.
Another factor that tends to push up the price of cable harnesses: In future data-driven business models, some functions may only be temporarily enabled via OTA software updates. In the case of electric vehicles, this can also include the motor performance. For car manufacturers to be able to implement such functions, the cabling must be designed for the maximum possible performance, even if this is rarely required at all. This will also make cable harnesses more expensive, Hornfeck explained.
On the other hand, there are also areas in which costs can fall. These include, for example, the trend to integrate power electronics directly into electric motors. Then OEMs could eliminate the 3-phase cables for power transmission (see diagram), Hornfeck said.
Leoni believes that the overall harness price will fall
through the electrification (C) Leoni AG
Cost reduction potential also arises from the centralization of computer resources and innovative approaches to vehicle operation. For example, functions are increasingly no longer activated and deactivated with a dedicated switch, but via a context-sensitive user interface. This can reduce the number of switches and operating elements – and, of course, the lines leading to these switches. “The vehicle electrical system will become simpler and less monolithic,” explained Hornfeck. “This allows the cable harnesses to be more modularized. This facilitates automated production.”
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