1. Introduction to DC Charging Piles

Unlike AC charging piles, ev charger dc convert alternating current (AC) into direct current (DC) and directly charge the electric vehicle's power battery without requiring conversion by the vehicle's onboard charger (OBC). As a result, the charging speed is significantly faster. For example, a typical electric vehicle with a 60 kWh battery may take over 6 hours to fully charge using an AC charging pile, but only about 30 minutes with a dc charger ev . The input voltage for ev charger station dc is three-phase four-wire 400 Vac ±15%, with common power ratings including 30kW, 60kW, 80kW, 120kW, 160kW, 180kW, and 240kW.

2. Main System Modules

2.1 Charging Module

Charging module is the core component of commercial ev charger equipment for new energy vehicles, and it is the basic unit to realise power conversion such as rectification, inversion and filtering. Its primary function is to convert AC power from the grid into DC power suitable for battery charging.

2.2 Control System

Includes the main MCU, charging controller, billing unit, communication module, etc.

2.3 Human-Machine Interface (HMI)

Touchscreen, status indicators, emergency stop button, card reader, etc.

2.4 Safety Protection System

Insulation detection, leakage protection, temperature monitoring, electronic locking, etc.

2.5 Air Cooling System

Dust-proof filters, high-power cooling fans, etc.

3. Working Principle

The electrical part of DC charging pile consists of primary circuit and secondary circuit. The input of the main circuit is three-phase AC power, which is converted into DC power acceptable to the battery by the charging module after inputting the circuit breaker and AC smart energy meter, and then connected to the fuse and charging gun to charge the electric vehicle. The secondary circuit consists of charging pile controller, card reader, display screen, DC meter and so on. Provides "start/stop" control and "emergency stop" functions. Signal lights indicate "standby", "charging" and "fault" statuses. The display screen serves as the HMI for operations such as card swiping, charging mode settings, and start/stop control, or for interacting with the charging pile via a mobile App.

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

4.1 Physical Connection

• ✅ The physical connection is the first step in DC charging of an electric vehicle. More charging failures occur during the physical connection or parameter configuration stage, resulting in failure to charge or failure to start charging.
• ✅ Insert the charging gun of the DC charging pile into the charging port of the electric vehicle completely, and the charging pile will judge whether the charging gun and the electric vehicle are fully connected through the voltage of the detection point on the circuit after connection. After confirming that the interface is fully connected, the electronic lock of the charging gun is locked and the vehicle should be in a non-driveable state as required by the national standard.

4.2 Low-Voltage Auxiliary Power-Up

The DC charging pile supplies 12V auxiliary power to the vehicle's BMS via the charging gun.

4.3 Handshake Phase

• ✅ Handshake start-up phase: DC charging pile sends charging pile handshake message to vehicle BMS, BMS sends BMS and vehicle handshake message to pile end after receiving handshake message, and completes insulation detection.
• ✅ Handshake identification stage: DC charging pile sends charging pile identification message to vehicle BMS, BMS receives handshake message and sends BMS and vehicle identification message to pile end, and enters parameter configuration stage.

4.4 Parameter Configuration Phase

• ✅ BMS sends battery charging parameter telegrams to the charging pile regularly, which contain information such as permissible charging voltage, current, capacity, temperature and SOC of the battery.
• ✅ After receiving the charging parameter message from BMS, the charging pile sends the maximum output capacity parameter of the charging pile to BMS, which contains the maximum and minimum output voltage and the maximum and minimum output current of the charging pile.
• ✅ BMS sends battery charging readiness message to the charging pile, the charging pile receives it and sends charging pile output readiness message to BMS, after BMS receives charging pile output readiness message, it enters the charging stage.

4.5 Charging Phase

• ✅ BMS sends BCL (Battery Charger Link), BCS (Battery Charging System) and BSM (Battery System Manager) messages to the charging pile periodically, and the charging pile sends CCS (charging status of the charging pile) messages to BMS periodically.
• ✅ According to the telegram information, the pile end judges in real time whether the battery status is normal or not, and judges in real time whether the pile end meets the charging end conditions. Vehicle side judges whether the voltage and current are normal in real time, and judges whether the vehicle side meets the charging end condition.

4.6 Charging Termination Phase

• ✅ During the charging phase, the charging module receives a command to stop charging and then switches off the output of the module and performs a discharge action; after that, the charging process enters the end-of-charging phase.
• ✅ When charging is completely finished, the electronic lock is released and a charging bill is generated.
• ✅ Charging is suspended under abnormal conditions:
  1. Charging post failure;
  2. Vehicle failure;
  3. Communication timeout;
  4. Abnormal state of mechanical S-switch;
  5. Electronic lock failure;
  6. Output voltage exceeding permissible battery voltage.