Electric vehicles are uniquely positioned compared with traditional gasoline. And the AC charge point plays an important role in automotive power solutions. It adopts onboard chargers for battery charging, with characteristics of low cost, simple structure and battery friendly compared to DC piles, which can be applied to a wide area for popularization. Today we will take a brief Introduction to charge pile technologies.
Interface Technology of AC charging interface
In an emergency, the battery can fully charge 80% of the maximum capacity within 15 minutes, and the corresponding charging rate should be 2C~4C. That belongs to the fast charging scheme, and the supporting public facilities are DC charging piles. DC charging pile is harmful to the battery, thus increasing the battery replacement cost. It is recommended to apply the DC Charging point when urgent.
The AC charging pile is designed to draw out single-phase or three-phase electricity. The charging pile only plays the role of a current transfer station, while the vehicle charger does the subsequent rectification + DC/DC conversion.
Based on the original AC charging, the AC charging post-interface technology is equipped with commercial modules, including human-machine interface, billing module, alarm module, and control guidance circuit, which is the core content of the AC charging post-interface technology. The international standard AC charging post interface features a 7-terminal structure compatible with both single-phase and three-phase power.
However, the length of charging time and battery life is still disturbing question. It is difficult to unilaterally optimize charging time or battery life caused of the size of the charging rate in the field of pure electricity. The larger charge and discharge rate, the smaller number of cycles. In addition, the charge rate should range from 0.5C~0.25C to ensure that the cycle charge times of the battery range between 800~1000.
Typical control guide circuit diagram of the connection mode
The control pilot circuit performs the function to confirm whether the interface and socket of charging are connected and then to perform periodic detection during the charging process to determine whether to continue or to stop.
Working Principle of Control Pilot Circuit
The Vehicle Control Unit confirms whether the vehicle plug and socket are connected by detecting the resistance value between PE and the monitoring point.
The power supply controller on the charging post side determines whether the power supply plug and socket are well-connected by voltage value detection of the monitoring and testing points.
When both the vehicle interface and power supply interface are confirmed to be connected, the charging pile switches S1 from the 12V connection state to the PWM state, waiting for the switch closure of the vehicle control unit.
In addition, the peak voltage of test point 1 is 9V, and the PWM wave of 1KHz is generated at the CP terminal, whose duty cycle represents the rated current of the charging pile. When the vehicle side switch S2 is closed, the vehicle is ready for charging. The peak voltage of detection point 1 is 6V. After confirming to ready, the vehicle charging pile closes the contactor K1 and K2 to turn on the AC circuit, and charging starts.
During the charging process, the EV charger performs periodic detection of the point detection to ensure the connection status of the charging connection device and whether the vehicle is in a chargeable state.
Equipped with a reliable grid power supply, the vehicle charger application for power battery charging belongs to the slow charging program, supporting the public facility’s AC charging pile.