Handbook of basic knowledge of new energy vehicle charging

Handbook of basic knowledge of new energy vehicle charging

1, what are slow-filling piles, domestic piles and fast-filling piles?

Fast charging pile (DC): DC is used for charging, and electric energy is directly stored in the power battery. High power, fast charging speed, and high requirements for power grid load are generally built and maintained by specific operators or car companies. Mainly used in scenes that need fast power supply.

Slow charging/household pile (AC): AC power is converted into DC by car charger, and then stored in power battery. Low power, slow charging speed, general household power grid can be added with a little modification, and the corresponding workload and installation cost are also low, so private charging piles are basically slow charging piles. Mainly used in scenes with fixed charging time, such as working hours and low electricity price at night.

2. What determines the power of slow-filling piles, domestic piles and fast-filling piles?

The nature of the charging pile itself will naturally affect the charging speed. Because the output voltage and current of charging piles of different operators are different, the charging power is also different.

Fast charging piles generally charge the battery in the car with large DC, which is the most basic factor different from slow charging/household piles. The current of fast charging pile can generally reach 150-300A, and the charging power can generally reach above 40kW. The current of the slow charging pile is basically at the level of 1-50A, so the household wall-mounted charging pile for pure electric vehicles is basically at the level of 32A/220V, which is about 7kW.

In addition, the charging power of household piles for plug-in hybrid electric vehicles is 3.3kW, that of household piles for pure electric vehicles is about 7kW, and there are two common types of slow charging piles, 3kW and 7kW. At present, the most common one on the market is 3kW.

Charging rated power and actual power are two concepts. The rated power marked on the charging pile and the charging power written in the vehicle manual are both theoretical values, and the actual charging power is also affected by many factors. For example, the electricity environment near the charging pile is also a factor affecting the charging speed of electric vehicles. For example, during the peak period of electricity consumption in summer, if the fast charging pile takes electricity from a nearby public transformer, the voltage will naturally decrease gradually with the increase or peak of the transformer load, so the charging speed will naturally slow down at this time.

Moreover, charging is the interaction between charging piles and electric vehicles. The battery capacity, battery temperature and BMS of the vehicle will all lead to different charging speeds. Of course, BMS is from the perspective of protecting batteries. Generally, the peak charging power appears in the middle section, and trickle charging will be carried out when the SOC exceeds 90%. At this time, the current and power will be reduced to prevent overcharging and overheating, thus achieving the purpose of protecting the battery.

3. Why can plug-in hybrid PHEV only be charged slowly?

First of all, due to the small battery capacity of PHEV models, the fast charging function is a bit weak. At present, the battery capacity of most plug-in hybrid vehicles is between 10- 15kWh. After all, electric drive is mainly auxiliary in the vehicle power system, mainly in the initial stage, and the demand for charging is not as strong as that of pure electric vehicles. If you use the fast charging function, you can charge quickly from 0-80%, but in the end, the 20% BMS battery management system will control the charging current to prevent overcharging and overheating, so the time of full charging is not much different from that of slow charging.

Secondly, considering the cost and vehicle architecture, plug-in hybrid vehicles have two sets of drive systems: fuel and electric. If fast charging is needed, it is necessary to increase high-voltage electronic equipment. At the same time, high voltage will cause strong current to batteries and electrical equipment, which will lead to heat generation, improve heat dissipation capacity and increase the investment of technical cost. The cost of plug-in and hybrid cars is difficult to control. If the fast charging system is added, it will inevitably lead to an increase in cost, further raising the cost of car purchase, thus affecting terminal sales.

4. What is the three-phase electricity that you often hear now?

Generally speaking, three-phase alternating current is a transmission form of electric energy, referred to as three-phase electricity. Three-phase AC power supply consists of three AC potentials with the same frequency, equal amplitude and phase difference of120.

Three-phase alternating current has many uses, and most industrial alternating current electrical equipment, such as motors, adopts three-phase alternating current, which is commonly called three-phase four-wire system. In daily life, single-phase power supply is often used, which is also called lighting power consumption. When lighting is powered by electricity, one of the three-phase electricity is used to supply power to electrical equipment, such as household appliances, and the other is the fourth line of three-phase four wires, that is, the zero line, which leads out from the neutral point of three-phase electricity.

5. So, does the new energy vehicle need to be connected with three-phase electricity for charging?

For the fast charging pile, the input must be three-phase electricity, because the power is too high, only three-phase electricity can drive it. For example, DC charging piles are powered by three-phase four-wire system, which can provide enough power, and the adjustable range of output voltage and current is large, which can meet the requirements of fast charging.

But for ordinary slow-filling piles and household piles, the input of charging piles is mostly single-phase, but there are also three-phases. Generally speaking, the power supported by single-phase electricity is low and that supported by three-phase electricity is high. The national standard household charging piles are basically 220V single-phase, with a maximum power of 7kW. However, you can also apply for a 380V30kW three-phase meter, including three-phase wires (red live wires), 1 blue neutral wire and 1 blue yellow double-color grounding wire, from which any red phase wire, a blue zero wire and a blue yellow double-color grounding wire can be led out to form 220V single-phase electricity. The specific installation depends on the permission of your area or property.