The main difference between electric vehicles and fuel vehicles is that the power source is different. Traditional fuel vehicles are refueled, while electric vehicles need to be charged. This article introduces the basic knowledge of electric vehicle charging equipment and charging.
1. Introduction of EV charger
The appearance and performance of charging equipment vary widely. We often hear names such as portable, household, fast charging, public/operating, etc. In addition, the interface of the charger also has AC charging interface, DC charging interface and so on. For charging practitioners, there are also a bunch of more confusing terms such as: Level 1/2/3, Mode 1/2/3/4, etc. The summary is that there are too many technical terms, which makes people dazzled. This article tries to give you an easy-to-understand overview of the concept of charging.
Charger is a common name for EV power supply equipment (Electric Vehicle Supply Equipment – EVSE), which is a tool for supplementing electric energy for electric vehicles, similar to refueling equipment for fuel vehicles.
Unlike refueling, which can only be done at gas stations, electric vehicles can be charged at home or at charging stations outside. Of course, you need a charging device. What kind of charging equipment is needed for what kind of electric vehicle, and what is the difference between the complicated charging equipment?
We first classify chargers according to different angles.
1.1. Classification of charger
1.1.1. Basic classification
Essentially, EV chargers can be divided into just two categories: AC (smart extension cords), and DC “true” chargers.
Figure 1 shows the principle of EV charging. The gray part on the left is the current flow of AC charging, and the green part on the right is the path of DC charging. It can be seen that the alternating current (AC) pile supplies power for the on-board charger (OnBoard Charger: OBC), and the on-board charger performs AC-DC rectification conversion to charge the power battery; while the direct current (DC) pile bypasses the on-board charger (OBC) Charge the battery directly.
The reason is simple. The power battery of an EV can only receive direct current (DC) current and voltage, while the power grid/household socket provides alternating current, which cannot directly charge the battery of the car. It needs to be converted from AC to DC, and the converted DC power can Charge the battery. All alternating current (AC) charging piles are just power supply lines for charging equipment (OBC), although they may be very smart power supply lines; while direct current (DC) piles integrate power modules, and AC-DC conversion is performed in the piles, and the output direct current is Charging batteries.
1.1.2. Standard classification
Unfortunately, as of today, there is no unified world standard for the charging interface of electric vehicles, just as the charging interface of mobile phones before 2012 is as complex and diverse.
Refer to Figure 2 for the interface types around the world. Charging cables of different standards and car-end charging interfaces cannot be used universally.
Generally speaking, the current standards are formulated by countries with auto industry and important market countries: Europe/America/Japan/China. There are 3 standards for the AC charging interface: Type 1 in the United States/Japan, Type 2 in Europe, and GB/T in China. There are four standards for DC charging interface, namely: CCS 1 in the United States (North America), CHAdeMO in Japan, CCS 2 in Europe, and GB/T in China. The rest of the world basically follows the US/European standards.
1.1.3. Power classification
Chargers range in power from 1kW to 500kW. Generally, the power levels of common chargers include 3kW portable devices (AC); 7/11kW wall-mounted Wallbox (AC), 22/43kW operational AC column devices, and 20-350 or even 500kW direct current (DC) devices.
The (maximum) power of the charger is the maximum possible power it can provide for the battery. The algorithm is voltage (V) x current (A), and the three-phase is multiplied by 3. 1.7/3.7kW refers to single-phase power supply (110-120V Or 230-240V) chargers with a maximum current of 16A, 7kW/11kW/22kW refer to chargers with single-phase power supply of 32A and three-phase power supply of 16/32A respectively. Voltage is relatively easy to understand. Household voltage standards in various countries, and current are generally the standards of existing electrical infrastructure (sockets, cables, insurance, power distribution equipment, etc.). The market in North America, especially the United States, is quite special. There are many types of sockets in American households (shape, voltage, and current of NEMA sockets), so the power levels of household AC chargers in the United States are more abundant, and we will not discuss them here.
The power of the DC device mainly depends on the internal power module (internal parallel connection). Currently, there are 20/30/40kW modules in the mainstream, so the power of the DC device is a multiple of the power of the above modules. However, it is also considered to match the charging power of electric vehicle batteries, so 60/120/240kW DC chargers are very common on the market.
1.1.4. Voltage/Mode Classification
There are different classifications for electric vehicle charging equipment in the United States/Europe. The United States generally uses Level 1/2/3 to classify; while outside the United States (Europe) generally uses Mode 1/2/3/4 to distinguish.
Level 1/2/3 is mainly to distinguish the voltage of the input terminal of the charger. Level 1 refers to a charger directly powered by an American household plug (single-phase) 120V, and the power is generally 1.4kW to 1.9kW; Level 2 refers to a charger powered by an American household plug (single phase). High-voltage 208/230V (Europe)/240V AC chargers have relatively high power, 3kW-19.2kW; Level 3 refers to DC chargers.
The classification of Mode 1/2/3/4 mainly depends on whether the charger communicates with the electric vehicle.
Mode 1 refers to the electric wire to charge the car. One end is a common plug connected to the wall socket, and the other end is the charging plug of the car. There is no communication between the car and the charging device (there is no device in fact, only the charging cable and plug). Now many countries Charging of electric vehicles in Mode 1 mode is prohibited.
Mode 2 refers to a portable AC charger that is not fixedly installed. There is communication during the charging process;
Mode 3 refers to a fixed installation (wall or column) AC charger. There is communication during the charging process;
Mode 4 refers specifically to fixed-installed DC chargers, and also has communication.
There are other classifications. For example, AC chargers are classified according to single/two/three-phase input power supply. The corresponding charging pile input terminals need to be connected to single-phase, two-phase and three-phase AC power supply respectively, and the number of output phases is the same as that of the input. The DC pile is generally powered by three-phase AC input.
In addition, there is a difference between private piles and operations. The former does not require charging and billing, while the latter requires charging and charging. Therefore, it is necessary to have a human-machine interface, a payment method, and a connection with the operation/tolling system.
2. Characteristics of electric vehicle charging
The charging power of electric vehicles is not constant, and the characteristics of lithium batteries determine that the charging curve is variable. Simply put, it can be divided into constant current charging, constant voltage charging and floating charging in the final stage.
Therefore, the process of fully charging an electric vehicle is longer than the charging time obtained by simple division calculation (battery capacity kWh/charger power kW).
Figure 5 is a curve for charging a standard EV battery.
3. Common Misconceptions about Electric Vehicle Charging
3.1. To shorten the charging time, need to choose a higher power charger?
The answer is not necessarily. It can be seen from the AC/DC charging diagram shown in Figure 1 that if it is AC charging, the AC charger is only a power supply device, and the real charging power is determined by the car charger (of course, the power of the charger is lower than that of the car charger. machine, the bottleneck is the charger). At present, the mainstream on-board chargers are 3/7/11/22kW, so if a 22kW AC converter is used to charge an electric vehicle with only a 3kW power OBC, the final charging power is still 3kW.
3.2. Can it be charged at full power with a DC charger?
The answer is not necessarily. Although there is no limitation of the on-board charger OBC, the DC directly charges the battery, but the upper limit of the battery needs to be considered, and the maximum power that the battery can support is also limited. Most non-high-end electric vehicles have the highest battery support. The charging power does not exceed 150kW. Even if it is charged on a 350kW super fast charge, the charging power cannot exceed the maximum power allowed by the battery (BMS). Of course, the charging power of different charging stages is also different.
At present, only a few high-end electric vehicles support relatively large charging power. For example, Porsche Tycan supports a maximum charging power of 225kW, and Audi’s E-Tron supports a maximum charging power of 150kW.
4. Points to note when purchasing a charger
Everyone is more concerned about how to buy an electric car when they have the conditions to install a home charger.
At present, AC is mainly used for home use (the price and power of DC chargers limit its installation in ordinary homes), first confirm the upper limit of the power allowed to install chargers at home (confirm the power distribution capacity of the home/community with the power supply company/property/electrician) ), and confirm whether the household is single-phase (domestic) or three-phase (European), and then confirm whether the electric vehicle on-board charger (OBC) purchased is single-phase (domestic electric vehicle OBC is mostly single-phase) or three-phase, Finally, buy the corresponding single-phase/three-phase charger. Theoretically, both single-phase and three-phase chargers are compatible with single-phase and three-phase on-board chargers, but if there is a single-phase OBC on board, there is no need to install a three-phase charger at all.
In addition, you need to consider choosing smart or fool. Smart is a charger that can be controlled by mobile app/identity authorization/charging management, and fool is that there is no human-computer interaction, and it can be charged by swiping a card or directly inserting a gun. The smart device is the first choice, which can be more convenient to control (such as regular charging, remote charging, etc.), charging record management, etc. will provide many conveniences, and there are also urban power grids (Germany) that stipulate that newly installed home chargers must be smart.
To sum up, in China and countries with single-phase household electricity, single-phase 7kW household chargers are basically the mainstream; in European countries/regions with three-phase household electricity, three-phase 11kW is the best choice. A smart charger with mobile app control is preferred.
Xuchang Jiachuang New Energy Technology Co. , Ltd.
Professional EV Charging Solution Provider