Failure Analysis of Electric Vehicle AC Charging Piles

As new energy electric vehicles become increasingly popular, the number of supporting public charging piles is growing year by year. Whether the measurement value of AC charging piles for electric vehicles is accurate is directly related to the vital interests of the vast number of electric vehicle owners. So, conducting regular mandatory inspections of charging piles is particularly important. Below, combined with relevant regulations and practical work, I’ll share some experience and practices on properly carrying out verification, fault analysis, repair, and correct maintenance of AC charging piles for electric vehicles.

1 Common Faults of AC Charging Piles for Electric Vehicles

During the use of AC charging piles, the main circuit is directly affected by current and voltage stress, which is the main cause of faults in AC charging piles. In terms of fault states, there are mainly two common situations for charging piles.

1.1 The power indicator of the charging pile is not on and it can’t charge
1.1.1 Fault Causes

A possible fault cause is that the charging power connection is abnormal：

The AC charging connection device is not properly connected; there is a fault in the charging pile circuit.

1.1.2 Fault Diagnosis & Troubleshooting

Diagnosis flow as Figure 1.

• Check distribution cabinet main switch (closed in normal operation; close if open).

• Test main switch output voltage (L - N, L - PE should be 220V). Abnormal voltage → check/reconnect circuit or replace switch (open, loose, damaged).

• Test charging pile input voltage (L - N, L - PE should be 220V). Abnormal voltage → reconnect circuit or replace switch (open/damaged).

1.2 Physical Connection Done, Charging Started but No Charge

Occurs when power, plug - battery connection, and standby state are normal. 7 cases:

• Normal charge but monitoring data shows 0 → Communication fault between pile & system.
  Fix: ① Restart monitoring/server; ② Reboot pile display; ③ Power - cycle display system & program.

• Charge current <20A (normal state) &rarr; Display/program fault.
  Fix: ① Restart display program; ② Power - cycle pile & program; ③ Reinstall display/program.

• Can&rsquo;t charge/enter interface &rarr; Communication fault.
  Fix: ① Check display parameters; ② Power - cycle display system/program; ③ Reinstall display/program.

• No BMS communication after display reboot &rarr; Communication fault.
  Fix: ① Power - cycle display system/program; ② Reinstall display/program; ③ Replace CAN bus module 200T.

• BMS normal, voltage normal but 0 current &rarr; Mistaken emergency stop press.
  Fix: ① Release emergency stop; ② Check battery & BMS.

• BMS normal, no charge voltage &rarr; Mistaken emergency stop press.
  Fix: ① Release emergency stop; ② Check battery & BMS.

• BMS normal, voltage fluctuates, 0 current &rarr; Charging module fault.
  Fix: Replace module.

2 Proper Use & Maintenance of EV Charging Piles

• Pre - charge: Inspect equipment (cables, connectors) for damage.

• Abnormality during use: Press emergency stop &rarr; cut all power.

• Keep flammables/explosives (gases, chemicals) away.

• Don&rsquo;t use if gun/cable has defects (cracks, wear, exposed wires).

• Never unplug during charging; no live - contact with gun core.

• Avoid outdoor charging in rain/thunder. Prohibit charging if water nears vehicle height.