I've noticed many industry colleagues are confused about the difference between high-voltage and charging cables for electric vehicles. This article will discuss the differences between the two from the perspective of electric vehicle high-voltage cable standards. In the charging station industry, cables are generally divided into two categories: one, typically used within electric vehicles, encompassing both high-voltage and low-voltage lines; the other, used for charging stations. Let's explore these in detail.
Introduction to High-Voltage Cables for Electric Vehicles
Electric vehicles primarily fall into three categories: pure electric vehicles, hybrid electric vehicles, and fuel cell vehicles. Pure electric vehicles and fuel cell vehicles are driven entirely by an electric motor, while hybrid electric vehicles combine an internal combustion engine with an electric motor, providing support during acceleration and low-speed conditions when the internal combustion engine is less efficient.
They all share a common driving voltage of 600V or higher. When it comes to wiring, they all share the same basic requirements: safely transmitting high current and voltage while maintaining EMI (electromagnetic interference) protection.
High-voltage cables are used to connect high-voltage batteries, inverters, air conditioning compressors, three-phase generators, and electric motors, enabling the transmission of power and electrical energy.
The basic principles of electric vehicles appear simple. However, a closer look reveals that system manufacturers face a host of challenges. New technical requirements are being placed on electric vehicle high-voltage cables, including flexibility, shielding, safety, and dimensions, as these impact the routing of high-current and high-voltage components. Each powertrain's distinct technical requirements also place specific demands on the required components.
It should be noted that electric vehicle high-voltage systems are not typical high-voltage systems. Terms such as "high voltage" and "high current" must be used within the automotive context, in contrast to the low-voltage systems of conventional vehicles.
Other sectors utilize completely different standards for their reference systems. For example, the definition of high voltage in the power sector begins at several thousand volts. (Cable Bao - Guaranteeing Product Quality, Money Safety, and Fair Transactions - www.dianlanbao.com)
Electric Vehicle High-Voltage Cable Standards
To address the aforementioned challenges and requirements for high-voltage cables used in electric vehicles, it is necessary to establish new cable standards to meet the needs of suppliers, wiring harness manufacturers, and OEMs.
This work is being carried out by the International Organization for Standardization's Technical Committee for Road Vehicles, Subcommittee on Electrical and Electronics, Working Group on Automotive Cables (ISO/TC 22/SC 3/WG4).
ISO 6722, based on the common 60 V cable standard, has been revised to meet the requirements of 600 V cables. Most of its requirements remain generic, but often fail to consider the specialized designs required for high-voltage cables. Similar revisions have also been made to ISO 14572.
Currently, the standardization of high-voltage cables exceeding 600 V is a topic within various working groups. The standard is ISO 17195.
SAE will adjust the requirements for high-voltage cables in the current high-voltage (rated 600 V) specification, SAE J1654, to cover rated voltages from 600 to 1000 V. A new, yet-to-be-published standard, SAE J2840, will define shielded cables.
LV is a common procurement specification among Germany's five largest automotive companies. It has currently introduced the LV 216 standard for high-voltage cables for electric vehicles rated at 600 V. This standard covers both single-core and multi-core shielded cables.
my country's national automotive industry standard for high-voltage shielded cables is currently under development, with a rated voltage of up to 1000 V. (Cable Bao - Guaranteeing Product Quality, Money and Goods Safety, and Fair Transactions - www.dianlanbao.com)
Electric Vehicle High-Voltage Cable Color
According to relevant specifications, the extruded jacket should be a bright orange color, and special high-voltage warning markings may also be added as required.
Electric Vehicle High-Voltage Cable Standard Requirements
1. Voltage
The fundamental difference from conventional automotive cables is that the structure must be designed for a rated voltage of 600 V. However, if used in commercial vehicles and buses, the rated voltage can be as high as 1000 V. In comparison, cables currently used in internal combustion engine-powered vehicles are designed for a rated voltage of 60 V.
High voltage reduces power losses in the transmission system (P = I² × R) by using lower current, while maintaining the same system power (P = U × I).
2. Current
Because the cables connect the battery, inverter, and electric motor, high-voltage cables are required to transmit high currents. Depending on the power requirements of the system components, this current can reach 250A to 450A. Such high currents are rarely found in conventional vehicles.
3. Temperature
High current transmission results in high power consumption and component heating. Therefore, high-voltage cables are designed to withstand higher temperatures. Currently, there is a trend toward increasing temperature requirements.
In contrast, cables typically rated up to 105°C in current vehicles are sufficient, as long as they are not used in the engine compartment or other areas subject to higher temperatures. High-voltage cables for electric vehicles are typically rated for temperatures higher than this, such as 125°C or 150°C.
If the routing within an electric vehicle is unfavorable, OEMs may even require higher high-temperature resistance. Examples include near the exhaust pipe, in front of the motor, and behind the battery.
4. Service Life
The automotive industry typically designs cables for a service life of 3000 hours within a specified temperature rating. In recognized cable standards (such as ISO 6722 and ISO 14572), this value is typically used for long-term aging tests. Special customer requirements for high-voltage applications may exceed 3,000 hours, with cumulative operating time at specified temperatures even reaching 12,000 hours.
5. Shielding Effectiveness
High-voltage cables themselves do not require shielding, as they do not transmit data like coaxial cables. However, shielding is necessary to prevent or reduce high-frequency radiation generated by the system's switching power supply from being induced through the cable into surrounding components.
Unlike gasoline-powered vehicles, electric vehicles require three-phase AC power to control their motors. This energy-carrying sinusoidal voltage is equivalent to square wave pulse signals of varying frequencies. Because high-frequency pulses have sharp edges, they generate high-energy harmonics that are radiated into the surrounding area.
EMI issues can be fully addressed by using appropriate shielding methods. In some cases, a combination of different shielding types may be required to meet varying shielding effectiveness requirements.
6. Flexibility
Hybrid vehicle development often faces the challenge of incorporating additional electrical components into the space originally designed to accommodate the gasoline engine and its components within existing series platforms. Even without considering wiring, space constraints are foreseeable.
Additionally, routing cables and connectors requires space. This often results in tight bend radii.
Due to the inherent design of conventional cables, high bending forces are difficult to overcome. To address this, high-voltage cable flexibility is crucial. Only with a relatively flexible design can routing through the vehicle be easily achieved.
7. Bending Resistance
If the electric motor is located near the moving parts of the vehicle, causing the connected high-voltage cable to vibrate continuously, it must be designed to withstand high cyclic bending cycles to ensure good bending resistance.
8. Marking
Because high voltages pose increased application risks, various standards stipulate that high-voltage cables must be visually distinguishable from ordinary automotive cables, specifying a bright orange surface color. Warning messages and special markings, such as "Caution! High Voltage 600V" or a high-voltage lightning symbol, may also be printed.
Differences Between Electric Vehicle High-Voltage Cables and Charging Cables
There are ten key differences between automotive high-voltage cables and charging cables: different routing, heat resistance, EMI requirements, protective measures, physical property requirements, chemical resistance, size requirements, color requirements, number of cores, and international standards.
1. Different Routing
Cable routing generally refers to the way the cable is routed from the distribution box to the electrical equipment or another distribution box. Cable routing varies based on the specific environmental conditions.
Automotive high-voltage cables are fixed, with only a very small static bend radius at certain points. Charging cables are mobile, with a smaller dynamic bend radius.
2. Different Heat Resistance
The higher the heat resistance of automotive high-voltage cables, the better. The higher the heat resistance, the greater the current carrying capacity. Therefore, the starting temperature is 125°C, with higher temperatures ranging from 180°C (silicone rubber) to 200°C (fluororubber). Charging cables are generally exposed to the elements and should not be exposed to excessive heat, with a maximum temperature of no more than 70°C, as this can cause burns.
3. Different EMI Requirements
First, let's discuss EMI and EMC.
Electromagnetic compatibility (EMC) is a comprehensive assessment of the electromagnetic interference (EMI) and interference rejection (EMS) capabilities of electronic products. It is one of the most important indicators of product quality. EMC measurement requires both a test site and test equipment.
Automotive high-voltage cables have very high EMI requirements to ensure they do not affect in-vehicle communication and control functions and must comply with automotive EMC standards. During charging, the vehicle is stationary, so charging cables do not need to meet automotive EMC standards; they only need to meet the EMC standards for the relevant environment, such as gas stations and residential areas.
4. Different Protective Measures
Necessary protective measures must be taken around automotive high-voltage cables; charging cables, without protection, must withstand various impacts and UV exposure.
5. Different Physical Performance Requirements
Automotive high-voltage cables must meet automotive abrasion resistance requirements; charging cables must meet the crush resistance requirements for mobile cables.
6. Different Chemical Resistance
Automotive high-voltage cables must withstand various liquids that can come into contact with the vehicle; charging cables must withstand various liquids in the living environment outside the vehicle. 7. Different Dimensional Requirements
Automotive high-voltage cables are subject to space constraints and have strict dimensional requirements, requiring the smallest possible size. Charging cables, on the other hand, have no size restrictions and can be made thicker and larger.
8. Different Color Requirements
Internationally, the standard color for automotive high-voltage cables is orange; there are no color requirements for charging cables.
9. Different Cable Core Counts
Automotive high-voltage cables are typically single-core for ease of installation. Charging cables are typically multi-core cables, containing a high-voltage main line, a ground line, a low-voltage signal line, and even a dual-function communication line (CAN).
10. Different International Standards
International standards for automotive cables are developed by the ISO; international standards for charging cables are developed by the IEC.
