Charging an electric vehicle's lithium battery is a crucial process involving safety and efficiency. Properly connecting the charging power supply is essential for protecting the battery, extending its lifespan, and ensuring charging performance. Below are the detailed steps and precautions for connecting an electric vehicle's lithium battery to a charging power supply:

1. Charging Principle
The charging process of a lithium battery involves lithium ions moving from the positive electrode to the negative electrode. During charging, the battery's positive terminal is connected to the positive output terminal of the charger, and the battery's negative terminal is connected to the negative output terminal of the charger.

2. Charging Methods
Lithium battery charging methods are generally divided into two types: constant current charging and constant voltage charging.
Constant Current Charging: The charger charges the battery with a fixed current until the battery voltage reaches a predetermined value.
Constant Voltage Charging: Once the battery voltage reaches the predetermined value, the charger switches to charging the battery with a fixed voltage. The charging current gradually decreases until charging is complete.

3. Charging Interfaces
Electric vehicle lithium batteries typically use the following charging interfaces:
DC Socket: Direct current charging, mostly used by the vehicle's onboard charger.
AC Socket: Charging via the vehicle's AC/DC converter.

4. Charging Station: DC fast charging, providing high-power charging.

5. Charging Equipment: Charging equipment includes chargers, charging cables, charging guns, etc., and must conform to the charging standards and interface specifications of electric vehicles.

6. Connection Steps:
1) Safety Check: Ensure the charging equipment is undamaged and the battery and charger interfaces are clean and free of foreign objects.
2) Select Charging Mode: Select the appropriate charging method (fast charging or slow charging) as needed.
3) Connect Charger: Connect the charger's output to the electric vehicle's charging interface.
4) Connect Battery: Connect the battery's charging interface to the charger's input.
5) Check Connections: Confirm that all connections are secure and reliable, without looseness or poor contact.

6. Charging Process Monitoring:
1) Start Charging: Start the charging process according to the vehicle or charger's operating instructions.
2) Monitor Charging Status: Monitor the charging status through the vehicle's dashboard or the charger's display screen.
3) Avoid Overcharging: Ensure the power is disconnected promptly after charging is complete to avoid prolonged overcharging.

7. Charging Safety
1) Waterproof and Moisture-proof: Ensure a dry charging environment and prevent moisture from entering the charging port.
2) Ventilation and Heat Dissipation: The battery generates heat during charging, requiring good ventilation and heat dissipation.

3) Avoid High Temperatures: Do not charge in high-temperature environments, such as inside a vehicle under direct sunlight.
4) Use Original Charger: Use the original charger recommended by the electric vehicle manufacturer whenever possible.

8. Charging Cable and Charging Gun
1) Wire Diameter Selection: Select the appropriate wire diameter based on the battery's charging current to avoid overheating.
2) Charging Gun: DC fast charging typically uses a charging gun, which must be correctly inserted into the electric vehicle's fast charging port.

9. Battery Management System (BMS)
The BMS is a crucial component in the lithium battery charging process, responsible for monitoring and managing the battery's charging status and providing protection against overcharge, over-discharge, and short circuits.

10. Post-Charging Operations
1) Disconnect Power: Disconnect the charger and battery promptly after charging is complete.
2) Check Battery Status: Check if the battery is functioning normally, and for any abnormal heating, swelling, or other issues.

11. Maintenance and Care
1) Regular Inspection: Regularly check the condition of the charging port and charging cable to ensure a reliable connection.
2) Cleaning and Maintenance: Keep the charging port and contact points clean to avoid dust and corrosion.

Conclusion: Charging an electric vehicle's lithium battery is a complex process involving multiple stages. Proper connection to the charging power source and charging operation are crucial for protecting the battery, extending battery life, and ensuring charging efficiency.