If you are an engineer and you wish to know CHAdeMO’s technical strengths in more details, here is a quick overview.
Interlock of connector
- No voltage applied without a vehicle coupler being connected. Given that control power is supplied to EV contactors via a charger, EV contactors never close and there must be zero voltage unless a vehicle coupler is connected to the vehicle.
- Pre-charge Automatic Safety Check. An insulation test is conducted before charging every time. The circuit insulation and the short circuit between the charger and EV contactors are checked.
- Never release the lock during charging. During charging, the vehicle coupler is locked to the vehicle inlet via a mechanical latch, and the mechanical latch is locked by a electrical lock. Once charging is completed, an electric lock is released after confirming the voltage on a vehicle connector. It is not allowed to release the lock automatically in case the inlet voltage does not drop to a safe level due to the vehicle contactors’ welding.
Protection from electrical shock
- Separation of the power system and battery system via an isolation transformer
The isolation transformer inside the charger separates the AC system at the input side and the DC system at the output side, therefore, the output side is a non-earthed system. So the electric shock can be avoided if an earth leakage fault occurs on one of the DC lines.
- Electrical shock protection using a leakage current monitoring device
A leakage current monitoring device is installed at the DC side as well as the AC side and it shuts down input power to the charger as soon as leakage current is detected. The electrical shock protection in the DC-2 zone stipulated under IEC60479-1 was realized by combining the leakage current monitoring and immediate automatic disconnection.
Fail-safe of charging control
- Redundancy of the stop charging
The vehicle and charger monitor malfunction during the charging. In addition to this redundant monitoring, two communication lines (CAN signal and Pilot signal) from the vehicle to the charger are prepared to send a signal in case there is a malfunction detected at the vehicle side. This way, charging can be stopped even if one communication line is broken.
- Protection in case the grounding wire and pilot line is disconnected.
When the vehicle coupler is dropped out, the disconnection of the grounding wire and the pilot wire causes each Pilot signal to turn OFF, which puts a halt to the DC output immediately. So the electrical arcing never continues.
Protection of battery
Current control by vehicle ECU
EV is the master of the charging current control. The fast charger controls the output current responding to the charging current request from the EV through CAN communication on a real-time basis. This mechanism enables the most appropriate and fastest charging based on the battery performance and usage environment. In order to make this control possible, CHAdeMO specifies the requirements for the response performance, current ripple, voltage ripple, and measurement accuracy of the current and voltage.