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New Energy Vehicle DC Charging Pile Operation Guide From Drawing The Gun To Charging It
Although the process of how to charge an EV might seem simple—unplugging the charging gun, plugging it into the car, swiping a card, charging, ending the charge, unplugging the gun again, and hanging it back up—it actually involves several detailed stages to ensure proper and safe charging.
Typically, the charging process for non-vehicle-mounted DC charging stations is divided into six steps, as shown in the diagram below. Throughout each complete charging cycle, the charger and the onboard BMS (Battery Management System) frequently exchange data to monitor each other and ensure proper charging. This process is known as message communication, and it uses CAN communication.
The entire charging process of an electrically powered electric vehicle consists of six stages: physical connection completion, low-voltage assisted power-up, charging handshake stage, charging parameter configuration stage, charging stage, and end-of-charging stage.
The detailed charging process is as follows:
1.Power On
Power is supplied to the charging station with 380V three-phase AC input from the grid. Five cables need to be connected from the distribution side to the charging station: three-phase AC inputs U, V, W, ground line PE, and neutral line N. The cable specifications are determined by the input current size of the charging station.
After the three-phase AC power is connected to the charging station, the power indicator light on the panel lights up, indicating that the charging station is in “standby” mode. Inside the charging station, the auxiliary power supply and DSP (Digital Signal Processor) of the “charging module” are in working condition. The CAN communication port of the charging module is also active, constantly ready to receive messages from the charging station controller.
Most charging stations in operation remain in “standby” mode until they are needed.
2 .Unplugging the Charging Gun
Remove the charging gun from the “socket” or “fixed holder” on the charging station.
It is important to note that most charging stations are equipped with a “fixed holder,” which merely serves to securely place the charging gun without any electrical connection. Some charging stations use a “socket” design, where users need to “swipe a card or scan a QR code” to start the billing process before “unplugging the gun.” Otherwise, the gun is locked to the charging station. Although this design slightly increases the cost of the charging station, as sockets are more expensive than fixed holders, it has the clear advantage of preventing the charging gun from being moved or tampered with.
3.Plugging in the Charging Gun
Insert the charging gun into the vehicle’s charging port. The following set of images illustrates this process vividly. Without specific explanation, you might mistake it for refueling.
The above three steps complete the first stage of the overall charging process: physical connection. After inserting the charging gun into the vehicle’s charging socket, the mechanical and electronic locks engage to lock the charging gun. Mr. Wu Yuming, one of the main drafters of the GB18487.1 standard and a representative of NARI Group Corporation, explains this as follows:
Swiping the card or scanning the QR code is equivalent to giving a “Enable” signal to the charging pile. After receiving this signal, the charging pile controller begins to perform a series of actions related to self-test.
Neither of the above two standards explicitly proposes the node of swiping a card or scanning a two-dimensional code, but this action is obviously important for the operation of charging piles.
It is worth explaining that the current charging pile design, many manufacturers in order to reduce costs, most of the AC input to save the AC contactor, only three-phase air switch (plastic-case circuit breaker).
The advantage of an AC contactor is that at night, when the charging pile has no owner to charge for a long time, the AC input of the strong current can be disconnected, and the “charging module” is in a complete power off state. However, the secondary power supply is maintained to ensure that the charging pile controller is always in standby state, and the AC contactor is activated or disconnected by swiping the card or scanning the QR code.
4.Self-Check
During the self-check process, users will see a series of steps and progress bars displayed on the charging station screen. This process includes the three stages mentioned earlier: low-voltage auxiliary power on, charging handshake stage, and charging parameter configuration stage. During this process, the charging station performs insulation testing, using a discharge resistor to reduce the high voltage from the insulation test to below 60V. The auxiliary power supply of the charging station powers the BMS (Battery Management System), which begins to operate. Data exchange, handshake, and configuration of charging-related parameters occur between the charging station and the vehicle’s BMS (the BMS informs the charging station about the battery information).
During the self-check, the charging station controller executes a series of programs, causing three sets of switches on both the charging station and the vehicle to open or close in a sequence of actions.
5.Charging
Once everything is ready, the core of the charging station (the charging station controller) sends commands to the charging module, which starts working according to the specified output voltage and current, continuously charging the EV’s battery.
During the charging process, the BMS and the charging station controller communicate in real time. The adjustment of the output current by the charging module is subject to certain constraints as specified in standard 184871.
6.Charging Completion
There are three main scenarios that can trigger the end of charging:
A: Human Factors
1.Manually swiping a card to end the charging process.
2.Using an app to issue a stop charging command.
3.Physically disconnecting the three-phase AC input, which will also stop charging.
B: Charging Station Factors
Charging will be terminated under the following conditions:
1.The charging station encounters a fault that prevents continued charging.
2.Communication failure occurs. Three consecutive communication timeouts are considered a communication failure.
3.The physical connection between the charging gun and the vehicle is interrupted, including the switch S changing from closed to open, or the vehicle interface becoming disconnected.
4.The output voltage of the charging station exceeds the maximum allowable voltage for the battery.
C: BMS Factors
The vehicle experiences an issue that prevents it from continuing to charge, and the BMS sends a stop charging message to the charging station controller.
7.Unplugging and Storing the Charging Gun
After charging is completed, and once the charging station’s output voltage is discharged to below 60V, the electronic and mechanical locks will release. The user can then unplug the charging gun from the vehicle’s charging port and return it to the fixed position or socket on the charging station.
