Overview:
This article explains the "State machine" process used by charging stations to manage the flow of energy during an EV charging session. The process involves a series of states that guide the station's behavior, based on interactions with the EV and charge pass authentication. The states are monitored and displayed via the ACE Service Installer tool.
1. State: Authentication and Initial Connection
State Transition to A1:
The customer authenticates at the charging station using an RFID card or a compatible charge pass. The station verifies the charge pass and then opens switch S1, activating a 12-volt current over the Control Pilot (CP) line. This transition moves the system from Idle State E to State A1.
In ACE Service Installer, Socket 1 displays STATE A and confirms that the RFID card is authorized with the message: NFC AUTHORIZED.
2. State: Cable Connection to the Charging Station
System in State A1:
The customer plugs the charging cable into the station, maintaining a 12V signal over the Control Pilot (CP) line. The station detects the resistor on the Proximity Pilot (PP) line and calculates the maximum available power for the EV. Since the cable is only connected to the station and not yet to the EV, no PWM signal is generated at this stage.
The system remains in State A1 until the next step.
3. State: EV Connection Established
Transition to State B1:
When the customer plugs the other end of the cable into the EV, the Control Pilot (CP) line establishes electrical contact. Resistor R2 joins the circuit, causing the voltage to drop to 9V. The charging station detects the EV and transitions the system horizontally to State B1.
In ACE Service Installer, the status displays EV Connected. At this stage, the PWM signal has not yet started.
4. State: PWM Signal Initiation
Transition to State B2:
The charging station begins generating a PWM signal, fluctuating between +9V and -12V, depending on system installation, power settings, and impedance on the Proximity Pilot (PP) line. This transition moves the system vertically to State B2, indicating that the charging station is connected but charging has not yet started.
In ACE Service Installer, the status displays Ready for Charging.
5. State: Charging Commences
Transition to State C2:
Upon receiving the PWM signal, the EV reads the maximum available current and closes switch S2, integrating resistor R2 into the circuit. This causes the voltage over the Control Pilot (CP) line to drop to 6V. The charging station continues generating the PWM signal at this voltage.
The system transitions horizontally to State C2, indicating that charging has begun.
In ACE Service Installer, the status displays Charging Power.
6. State: Charging Process Monitoring
Continuous State C2:
While in State C2, the charging station continuously monitors the battery charging process. The system adjusts the maximum allowed power using the PWM signal as needed.
7. State: Session Interruption (RFID Swipe)
Transition to State C1:
If the RFID card is swiped during the charging session, the charging station halts the PWM signal while maintaining 6V on the Control Pilot (CP) line. The system transitions vertically to State C1.
The EV, not receiving the PWM signal, switches off switch S2, deactivating resistor R2, and causing the voltage to rise to 9V. The system then moves horizontally to State B1. The charging station cuts off power and unlocks the cable.
8. State: End of Session
Transition to State A1:
When the cable is removed, the Control Pilot (CP) line is interrupted, deactivating resistor R1. The system transitions horizontally to State A1, with 12V current over the CP line and no modulation, signaling that the charge point is ready for the next transaction.
9. State: Battery Fully Charged
Transition to State B2 (after Full Charge):
If the EV’s battery is fully charged, the EV deactivates resistor R2, causing the voltage to rise back to 9V. The PWM signal remains active at 9V, allowing the car to temporarily reactivate the resistor if needed. The system transitions horizontally to State B2.
Transition to State B1 (after RFID Swipe):
Swiping the RFID card will stop the PWM signal and unlock the charging cable. The system transitions vertically to State B1.
10. State: Reset After Cable Removal
Transition to State A1:
Once the cable is removed, the system returns to State A1 with a steady 12V over the Control Pilot (CP) line. The charge point is now ready for the next transaction.
Conclusion:
This article describes the state transitions involved in an EV charging session, focusing on the "State machine" process that governs how the charging station interacts with the EV and charge pass. Understanding these states is essential for effective troubleshooting and operational monitoring, with the ACE Service Installer tool displaying the system status at each stage.