Charging systems can be divided into two types: regular charging and fast charging. Visually, the charging ports are quite distinct: fast charging ports are large with nine holes (two large holes, one medium hole, and six small holes), while slow charging ports are smaller with seven holes (five large holes and two small holes). This makes it easy for even novice users to plug them in correctly. Generally, the two charging ports are located at the front and rear of the vehicle, although some models combine them, for example, at either the front or rear. Owners can choose the charging method based on their charging time requirements.
Fast charging
Fast charging uses DC charging. It requires a larger charging current, necessitating the construction of fast charging stations. It doesn't need to fully charge the battery; it only needs to meet the requirements for continued driving. In this charging mode, the battery only needs to be charged to 50% to 80% in 20-30 minutes. Ground-based charging piles (equipment) directly output DC power to charge the vehicle's battery; the electric vehicle only needs to provide charging and related communication interfaces.
Advantages of fast charging: shorter charging time, faster vehicle turnover, and reduced parking space required for charging stations.
Disadvantages of fast charging: Higher manufacturing, installation and operating costs of chargers; Large charging current, which requires advanced charging technology and methods, and has a negative impact on the lifespan of power batteries; It can easily cause abnormalities in power batteries, posing safety hazards, and high-current charging can impact the public power grid, affecting the power supply quality and safety of the grid.
Regular charging (
This charging mode is an AC charging method, in which the external power grid provides 220V household single-phase AC power to the electric vehicle's on-board charger, which then charges the power battery. A full charge typically takes 5 to 8 hours.
Advantages of regular charging: charging piles (charging boxes) are low-cost and easy to install; they can utilize off-peak electricity during the night to reduce charging costs; the charging current is relatively small and the voltage is relatively stable during the charging period, which can ensure the safety of the power battery pack and extend the service life of the power battery.
The disadvantages of regular charging are that the charging time is too long, making it difficult to meet the needs of vehicles in emergency operation.
fast charging interface
DC+: DC power supply positive
DC -: DC power supply negative
PE: Ground (Earth)
S+: Communication CAN-H
S-: Communication CAN-L
CC1: Charging connection confirmed
CC2: Charging connection confirmed
A+: 12V+
A-: 12V-
How do CC1 and CC2 confirm whether the connection is normal?
Below is a schematic diagram of the CC1 charging pile connection detection principle.
As shown in the diagram below, to determine if the connection is normal, you can check the voltage at the test point. Different voltages are obtained by voltage division using different resistors.
| Detection point 1S switch | ||
| Voltage | Gun head status | Gun head and base status |
| 12V | disconnect | disconnect |
| 6V | closure | disconnect |
| 6V | disconnect | Combination |
| 4V | closure | Combination |
Next is the schematic diagram confirming the connection of the CC2 vehicle control device.
When connected, the two resistors divide the voltage to obtain 6V; otherwise, 12V is obtained.
Taking the BYD e6 as an example, the vehicle body connection device is used to conduct and input external electrical energy into the power battery when the vehicle is charging. The charging port cover has damping characteristics, that is, to check whether the resistance value between "CC1" and "PE" on the charging port is 1KΩ; at the same time, it is necessary to check whether the connection from the charging port to the power manager is normal.
slow charging port
The "cable-on control box" and the "vehicle control device" confirm that their connections are correct.
First, the "cable-on control box" checks if the voltage is 12V through CP detection point 1 and detection point 4. If the connection is not correct, detection point 4 will not be grounded and no voltage will be detected. If the connection is correct, detection point 4 will be grounded to the vehicle through PE, and the voltage will be 12V. Once there is 12V, the "cable-on control box" will connect S1 to PWM; otherwise, S1 will be connected to +12V.
Next, the vehicle control unit will use the CC sensor to check the R3 resistor to confirm whether the charging gun is connected to the vehicle socket. If it is not connected properly, the resistance will be infinite; otherwise, it will have a corresponding resistance value.
Here, the vehicle control unit sets the on-board charger power (usually set by the manufacturer at the default setting):
The on-board charging device determines the maximum charging current of the control box on the cable by using the duty cycle signal of the CP. The general setting ratio is shown in the table below.
| PWM duty cycle D | Maximum charging current Imax(A) |
| D = 0% Continuous -12V | Charging stations unavailable |
| D=5% | A 5% duty cycle indicates that numbers are required. |
| Communication is required, and communication between the charging station and the electric vehicle should be recommended before the power supply. | |
| 10% ≤ D ≤ 85% | Imax = D * 100 * 0.6 |
| 85% < D ≤ 89% | Imax = (D * 100 - 64) * 2.5, and Imax ≤ 63A |
| 90% < D ≤ 97% | Reserved |
| D=100%, continuous positive voltage | Not allowed |
At the same time, the on-board charging device will also determine the rated capacity of the cable through the RC on the CC.
| RC | Charging cable rated capacity |
| 1.5kΩ | 0.5W 10A |
| 680Ω | 0.5W 16A |
| 220Ω | 0.5W 32A |
| 100Ω | 0.5W 63A |
Finally, after calculating the rated capacity of the charging cable and the current of the control box on the cable, the vehicle control unit sets the maximum power of the on-board charger to their minimum value.
After all that, some people will surely ask: "Why are there two charging ports? Wouldn't it be better to use only one?" This is mainly due to the fast charging technology.
It's important to understand that the vehicle charging process isn't simply a matter of charging from the grid to the battery. It involves passing through a charging station, charging cables, a charging plug, and the vehicle's charging socket before reaching the vehicle. As we've learned from the previous explanation, for AC charging, once inside the vehicle, it doesn't go directly to the battery; it still passes through the onboard charger and the Battery Management System (BMS).
For fast charging, compared to AC charging, there are no limitations on the specific charging voltage and current, ranging from 20kW, 40kW, 60kW to 200kW, 250kW, and 350kW. As long as the input (grid) and output (vehicle) support it, it can be made very large.
Electrical energy from the grid first enters the charging station, and then reaches the vehicle through the charging cable. Most of the charging cables are fixed to the charging station, and the other end is a gun-shaped plug that connects to the vehicle (this connection method is called connection method C in the standard).
A small number of charging stations are isolated and require a separate cable, with one end connected to the charging station and the other to the vehicle (Connection Method B). The method of fixing the charging cable to the vehicle (Connection Method A) is almost never used. AC charging can use both Connection Method B and Connection Method C, but AC charging currents greater than 32A and DC charging can only use Connection Method C.
Because the vehicle's electrical system is a DC system, AC power cannot directly charge the battery during AC charging. It needs to go through a component called an on-board charger (OBC) to convert the AC power to DC power and transform it according to the BMS commands before supplying it to the battery.
This diagram of an on-board charger shows two core components: an AC/DC rectifier and a DC/DC transformer (the power unit in the diagram). The former converts alternating current (AC) into direct current (DC) that is acceptable to the vehicle's battery, while the latter adjusts the voltage of the DC current.
Based on commands from the BMS, the charging current and voltage are dynamically adjusted to adapt to the charging needs of batteries at different stages. For example, during constant current charging, the charging voltage needs to increase as the battery capacity increases. It is also responsible for converting to low voltage to charge 12V small batteries.
In DC charging, the DC charging station itself is an AC-DC rectifier and a DC-DC transformer. It directly converts AC power outside the vehicle according to the needs of the BMS, replacing the function of the on-board charger. Therefore, DC charging stations are also called off-board chargers.
