Understanding the Root Causes Behind Random Charging Interruptions

Intermittent disconnections during AC EV charging—often searched as phrases like “EV charger keeps stopping” or “AC charging randomly disconnects”—can be challenging to diagnose. Based on IEC-compliant analysis and field experience, here are the most common causes:

1. 🏭 Power Grid Fluctuations: Weak Grid and Voltage Drop Effects

  • Voltage fluctuations beyond the operational range of the onboard charger (OBC) can trigger overvoltage or undervoltage protection.
  • Long cable runs from a 11kW/400V transformer may lead to a “weak grid” condition. In such cases, the OBC may experience current loop oscillation, resulting in input overcurrent protection.

2. 🌐 PE Ground Noise: How Electrical Interference Disrupts AC Charging

  • The vehicle chassis ground connects to the AC supply PE via the charging connector’s earth pin.
  • If many high-power devices are connected to the same PE ground, it can introduce noise. This affects CP (Control Pilot) and PP (Proximity Pilot) signal detection, and may cause CAN communication failures inside the OBC.

3. 🔌 Connector Fitment Issues: The Physical Link in Reliable EV Charging

  • 3.1 Loose Power Contacts: In some vehicles, prolonged charging causes the inlet contacts to heat up. Overheating may trigger temperature protection, causing the vehicle to stop charging.
  • 3.2 Signal Pin Mismatch: Poor contact between CP/PP pins and the vehicle’s socket (especially under vibration) may interrupt charging. Using longer CP/PP pins can improve compatibility with various sockets.

4. ⚡ False RCD Tripping in AC EV Chargers

  • Some Mode 2 and Mode 3 chargers include internal leakage detection PCBs. Improper design or calibration can lead to false positives, triggering RCD shutdowns unnecessarily.

5. 🙍 Human Error: Accidental User Actions That Interrupt Charging

  • Users may unintentionally press the stop button on the charging station or squeeze the S3 switch on the plug, causing the charger to interpret a disconnect command.

Conclusion: Random EV charging interruptions are typically caused by grid instability, grounding interference, poor plug contact, or misconfigured protection systems. To minimize dropouts, ensure proper PE grounding, use certified IEC-compliant hardware, and perform regular inspection of connectors and pins. For OEM/ODM solutions designed to resolve these real-world challenges, talk to our experts or explore our professional-grade AC EV chargers., ensure proper grounding, select certified hardware per IEC 62752 / IEC 61851, and evaluate environmental factors like temperature, grid quality, and plug fit. For OEM/ODM solutions that solve these real-world issues, talk to our experts.