Driven by global demand for reducing CO2 emissions and improving fuel efficiency, the research and development of electric vehicles has been promoted and advanced worldwide, aiming to replace traditional gasoline-powered vehicles. In fact, due to their low power consumption and zero local emissions, electric vehicles offer a relatively good option for mitigating the environmental impact of transportation and reducing dependence on energy.
Against this backdrop, the electric vehicle market has seen rapid growth since 2010, as shown in Figure 1. In 2018, the global electric vehicle fleet exceeded 5.1 million vehicles, almost double that of 2017. By the end of 2019, the global electric vehicle fleet, including light vehicles, reached 7.5 million vehicles. In 2020, the global EV fleet surpassed 10 million vehicles, a 43% increase since 2019. Notably, two-thirds of the existing fleet and all newly registered electric vehicles were pure electric vehicles. In 2021, EV sales reached a new high, nearly doubling to 6.6 million vehicles, bringing the total number of electric vehicles on the road to over 16.5 million. After several years of development, sales in China tripled compared to 2020, reaching 3.3 million vehicles, while in Europe, sales increased by two-thirds in 2021, reaching 2.3 million vehicles compared to 2023. In 2021, more than 85% of global electric vehicle sales came from China and Europe, more than doubling from 2020 to reach 630,000 units, followed by the United States at 10%. Figure 1 shows the global electric vehicle fleet from 2010 to 2021, and Figure 2 shows the global electric vehicle sales and market share from 2016 to 2021.
I. Fast Charging System
1. Introduction to Fast Charging System
Fast charging, also known as DC charging, refers to off-board chargers (fast charging stations) that convert AC power from the grid into high-voltage DC power to charge the battery pack. It has a large power output and can efficiently and quickly fully charge an electric vehicle in a short time.
Fast charging stations are generally used in highway service areas, bus stations, residential parking lots and other places. They are powered by 380V three-phase electricity and can reach tens of kilowatts and hundreds of kilowatts. Common models include 45kW, 60kW, 120kW, 150kW and 180kW. The output voltage platforms are 200-500V, 500-750V or 200-750V, and the maximum output current is several hundred amps.
2. Fast charging system components
The fast charging system consists of a fast charging pile, cable assembly, fast charging interface, and electric vehicle. It is connected to 380V industrial power grid, and the 380V AC power is converted into high-voltage DC power by the fast charging pile's conversion device. The DC power then enters the battery pack directly through the vehicle's fast charging port. The ECU unit of the fast charging pile communicates with the vehicle's BMS to ensure safety and reliability during the charging process.
3. Introduction to Fast Charging Interface
DC charging vehicle-side socket
The fast charging interface is only used to provide DC power. The fast charging interface consists of 3 power pins (DC+, DC-, PE) and 6 signal pins (S+, S-, A+, A-, CC1, CC2).
CC1 is the power supply connection. CC1 has no circuitry on the vehicle; it only exists on the charging dock. It is used by the DC charging pile to detect the vehicle's connection status. CC2 is the vehicle connection, used by the vehicle to detect the DC charging pile's connection status.
A+ and A- are auxiliary power supplies. When the gun and the pile are successfully connected, there will be 12V to wake up the BMS.
S+ and S- are for CAN communication. The vehicle's BMS uses these two lines to send battery charging demand parameters to the DC charging station in real time. The DC charging station then adjusts the charging voltage and current in real time based on these parameters. In addition, the charging station and the BMS also exchange their respective status information.
4. Fast charging working principle
The schematic diagram of the DC charging control guide circuit shows that switch S is a mechanical button on the charging gun. Switch S closes when the charging gun is fully connected to the vehicle socket. Throughout the charging process, the off-board charger control device should be able to detect contactors K1 and K2, and contactors K3 and K4. The vehicle control device is generally integrated into the battery management system (BMS) and controls contactors K5 and K6.
Test point 1 is tested by the off-board charging control device, and test point 2 is tested by the vehicle control device. R1=R2=R3=R4=R5=1000±3%Ω, U1=U2=12±5%V. The charging pile has an insulation detection circuit (IMD) and a discharge circuit.
The fast charging process can be summarized as follows.
II. Slow Charging System
1. Introduction to slow charging systems
The AC slow charging system connects to an AC charging station or a 220V household AC socket via a slow charging harness (either from a charging station or the vehicle itself). The on-board charger (OBC) converts the 220V AC power into DC power, thus replenishing the electric vehicle's power battery.
2. Components of the slow charging system
The charging system for new energy vehicles mainly consists of charging piles, charging harnesses, on-board chargers, high-voltage control boxes, power batteries, DC-DC converters, low-voltage batteries, and various high-voltage and low-voltage control harnesses.
3. Introduction to slow charging interface
When the vehicle is in AC charging mode, the on-board charger detects the CC and CP signals (charging gun insertion and conduction signals) of the AC charging interface and wakes up the BMS. The BMS then wakes up the on-board charger and sends a charging command, simultaneously closing the main relay, and the power battery begins charging. Charging time: Estimated 13-14 hours for a full charge.
4. Slow charging working principle
5. Charging conditions for AC slow charging system:
(1) CC and CP signals 135 connection 8509 is normal 9287. Mr. Fang
(2) The 220VAC power supply of the on-board charger (OBC) is normal, the OBC constant power supply is normal, and the OBC is working normally.
(3) OBC wake-up signal is normal.
(4) The vehicle-side VCU, instrument cluster, vehicle terminal, and BMS are communicating normally, and the positive and negative contactors are normal.
(5) The temperature of the power battery pack is greater than 0 degrees and less than 45 degrees.
(6) The voltage difference between the highest single cell voltage and the lowest cell voltage of the power battery pack is less than 300mV.
(7) The temperature difference between the highest and lowest temperature points of the power battery pack is less than 15 degrees.
(8) The insulation resistance of the vehicle is greater than 500Ω/V.
(9) The actual maximum single cell voltage is not greater than the rated voltage of the single cell by 400mV.
(10) The high and low voltage lines are connected normally and the remote scheduled charging switch is closed.
Note: Copyright belongs to the original author. The views expressed in this article are for sharing and exchange purposes only and do not represent the views or positions of this public account. If there are any copyright issues, please inform us and we will handle them promptly.
The principle, fault diagnosis, and troubleshooting approach for AC slow charging of electric vehicles
1. Before the charging gun is connected to the car, the CP signal is at a high level of 12V;
2. After the charging gun is connected to the car, the CP signal will jump to 9V due to the voltage divider resistor in the on-board charger;
3. After the charging pile MCU detects that the CP signal jumps to 9V, it switches the high-level output to PWM output;
4. PWM duty cycle indicates the maximum output current of the charging pile;
5. Once the car confirms the charging signal, it will switch the voltage divider resistor in the onboard charger, causing its signal to jump to 6V;
6. After the charging pile MCU detects that the CP signal has switched to 6V, the main relay closes and begins charging the vehicle;
7. During charging, monitor the amplitude of the PWM signal in real time. If the voltage drops to a value other than 6V, immediately disconnect the power.
