1. Introduction to AC Charging Piles

Differing from DC charging pile, AC pile is essentially a socket with control, the output is AC power, which needs to be converted into DC power by transformer rectifier through on-board charger. Due to the power limitation of the on-board charger, the power of AC pile is small. Therefore, the AC pile is only to provide power output, no charging function, play a role in controlling the power supply, and the charging time is slower, without the charging speed and effect of DC pile. The input voltage for AC charging piles is single-phase two-wire 220Vac ±15% or three-phase four-wire 400Vac ±20%, with common power ratings including 7kW, 11kW, and 22kW. Typically, it takes 5-8 hours to fully charge a vehicle's battery from 0%.

Although AC charging for electric vehicles is slower, frequent use of AC charging helps extend battery life and reduces the risk of overheating or malfunctions.

2. Main System Modules

2.1 Control System

The main control module is the core of the entire charging pile, playing a critical role. The main control board communicates with the touchscreen and LCD display, receives user operation commands and parameter configuration instructions, send real-time status information of the charging process and present it to the display.

2.2 Human-Machine Interface (HMI)

Includes the display screen, status indicators, emergency stop button, card reader, etc.

2.3 Safety Protection System

Surge protectors, leakage protection, temperature monitoring, etc.

3. Working Principle

The AC power output from the charging pile enters the vehicle's onboard charger (OBC) through a standard charging plug and socket. The OBC then converts the AC power into a DC voltage suitable for the power battery, completing the AC charging process. The main equipment involved in AC charging includes the AC charging pile, standard charging plug and socket, charging cable, onboard charger (OBC), vehicle control unit (VCU), and battery management system (BMS).

4. Charging Process Control Logic (Based on GB/T Standard)

• ✅ After inserting the charging gun of the AC charging pile into the vehicle's charging port, the vehicle checks the voltage at the monitoring point in the circuit to determine whether the charging gun is fully connected.
• ✅ The onboard charger detects the CC (Connection Confirmation) and CP (Control Pilot) signals. The OBC can determine the capacity of the charging cable based on the CC signal and assess the power supply capability of the charging equipment based on the CP signal. It then wakes up the VCU and BMS.
• ✅ Once awakened, the VCU and BMS enter AC charging mode and check the vehicle's status, including whether there are any faults or if the battery is fully charged.
• ✅ The onboard charger provides feedback to the BMS about the charging cable status and power supply information.
• ✅ Based on the information from the OBC and the vehicle's status, the BMS sends commands to start or stop charging to the onboard charger.
• ✅ The power control device of the AC charging pile uses the CP signal to determine the vehicle's status and controls the connection or disconnection of the AC power input.
• ✅ The onboard charger starts or stops working according to the received commands, charge the vehicle or stop charging to go to sleep.