When it comes to automobiles, besides traditional mechanical system, the most important thing is the electrical system. And the more high-end cars, the more complicated the electrical system. For automotive electrical appliances, mainly have the following characteristics.
1. Low pressure
The voltage of car electrical appliances is lower than the household voltage. There are generally only three rated voltages of 6V, 12V and 24V on cars. Modern small cars generally use 12V power supplies. Some heavy vehicles will use 24V power supply. However, some heavy-duty vehicles are limited by power and wiring. So, only diesel engine starting devices use 24V power supply. Other electrical equipment is still 12V power supply. The voltage of the power supply can only be changed by the power switch. The main reasons for using low voltage in automotive electrical appliances are safety and simple power supply.
2. DC
Automobiles use DC power is because they need to use batteries as the starting power source for engine power. The battery must also be charged with direct current after the electric energy is consumed. So, the electrical system in the car has always been direct current. The direct current of the automobile is the alternating current generated by the alternator. It is rectified by the rectifier inside the generator. And the voltage is regulated by the voltage regulator and then output.
3. Single wire system
There are two power sources: battery and generator. And all the electrical equipment on the car is connected in parallel. The electrical equipment is connected to the positive pole of the power supply with only one wire. Use metal bodies such as engine, body and frame as a common circuit. And it is connected to the negative pole of the power supply. The single-wire system has the advantages of clear wiring, less wiring, and convenient installation and maintenance. In some small cars, the two-wire system will be partially adopted. Wires are used to connect the negative poles of these electrical equipment to a common ground point. Or, they will be connected to a common ground wire. To ensure the safety of the vehicle's electricity use.
In order to use metal conductors such as the engine, body, and frame as a common circuit. One pole of the battery, generator, and other related electrical equipment must be connected to the engine. And also, it would be connected to car’s body, frame. So, it is called minus earth. The negative ground of the battery is connected to the car body. The connection between the positive electrode of the battery and the car body is called the plus earth. Modern automobile electrical appliances mostly use the negative ground connection method.
5. Parallel connection of electrical equipment
Various electrical equipment on the car is connected to the power supply of the car in parallel. It is the so-called parallel connection of electrical equipment. Each electrical equipment has a dedicated switch to control it, without mutual interference.
6. Equipped with safety devices
Safety devices are installed in the car circuits to prevent overcurrent. If the circuit has overcurrent, these safety devices will be disconnected before the harness and electrical equipment are damaged.
Because of these characteristics of automobile electrical appliances, people can safely use electrical appliances while driving.