control pilot CP

EV charging stations coordinate three flows—power, low-voltage cable signaling, and cloud data—so the vehicle and station agree on limits, close the contactors safely, deliver measured energy, and settle the session.     First-time user quick pathLocate a station → authenticate (RFID, app, or Plug and Charge) → plug in and watch the session start.     What a station actually doesA station is more than a socket. It routes safe power, exchanges low-voltage signals with the car to agree limits, talks to a backend to authorize and log the session, and produces a billable record. The process is controlled, measured, and auditable end to end.     The three flows in one viewPower: grid or on-site generation → distribution panel → cabinet or wallbox → contactor → vehicle batteryControl: control-pilot signaling (IEC 61851-1 / SAE J1772) advertises limits → vehicle requests within those limits → safe state reachedData: station ↔ cloud via a charging protocol (e.g., OCPP) for authorization, tariffs, session status, meter values, and receipt     AC vs DCWith AC charging, AC-to-DC conversion happens inside the car’s onboard charger (OBC) at modest power.With DC fast charging, conversion moves into the cabinet; rectifier modules supply high-current DC directly to the battery while the vehicle supervises demand and limits.     AC vs DC roles and signals Item AC charging (home & workplace) DC fast charging (public DC) Where AC→DC happens Inside the car (onboard charger) Inside the cabinet (rectifier modules) Typical power 3.7–22 kW 50–400 kW+ How current is set Vehicle requests within station limit Station modules meet vehicle request within site and thermal limits Bottleneck rule Session rate = min(vehicle capability, station capability, site limits) Session rate = min(vehicle capability, station capability, site limits) Cable and interface (by region) Type 2 or J1772 CCS2, CCS1, GB/T, or NACS On-cable signaling Control Pilot 1 kHz PWM declares current ceiling; Proximity Pilot identifies cable and latch Same low-voltage chain plus high-voltage interlocks and insulation checks Safety chain State transitions before the main contactor closes; leakage protection present Same chain plus pack-level protections Cloud link Session, tariff, status, faults, firmware Same, with more telemetry and thermal data     What happens on the wireBefore any high voltage appears, the station and vehicle talk over two low-voltage lines in the connector. The control pilot is a 1 kHz square wave; its duty cycle advertises the station’s current ceiling. The vehicle reads that ceiling and never requests more.   The proximity pilot tells the station what cable is connected and whether the latch is engaged. Only after these checks pass does the system move from a waiting state to an energized state. For readers who need the physical interface and handling notes, see our Type 2 EV connector page for shell geometry, latch behavior, and cable rating basics.     The safety chain that prevents hot-plugging Mechanical: the latch holds the plug in place; the station senses it. Electrical: ground and insulation checks pass; leakage protection is armed. Logical: once the vehicle signals readiness, the station transitions to the energized state. Power: the main contactor (high-power relay) closes; monitoring continues during the session. If any condition fails, the contactor opens and power stops.     How the station talks to the cloudStations rarely run alone. Through OCPP (Open Charge Point Protocol), the unit reports status, receives tariffs and updates, opens and closes sessions, and uploads meter values and error codes. Typical message flow includes Authorize → StartTransaction → MeterValues (periodic) → StopTransaction, plus Heartbeat and Firmware management. A certified meter records energy in kilowatt-hours; time-based or session fees can be added by policy, but the energy measure anchors the bill.     From plug-in to billing: a seven-step timeline 1. Physical connection: insert the connector until the latch clicks; the station senses cable type and capacity. 2. Safety checks: ground and insulation look correct; the station broadcasts the 1 kHz control signal. 3. Capability announcement: the duty cycle states the maximum allowed current for this outlet and cable. 4. Vehicle readiness: the vehicle acknowledges and requests an appropriate current or begins the DC handshake. 5. Energize: the station closes contactors; protective devices arm and stay vigilant. 6. Metered delivery: energy is measured and logged; limits adjust with temperature, load management, or site policy. 7. End and settle: stop via button, app, RFID, or target reached; logs are finalized for billing.     Why sessions fail more often than they should• Physical fit and latch: dirt, misalignment, worn seals, or a bent spring can block the proximity signal.• Cable and strain relief: sharp bends, damaged sheath, or water ingress trigger protection.• Signaling out of range: poor contact or corrosion alters low-voltage levels so the vehicle never sees a valid state.• Backend delays: if the cloud takes too long to authorize, the station times out.• Thermal limits: hot weather or a dusty filter derates current; some vehicles stop early to protect the pack. For high-duty public sites in hot weather, a CCS2 liquid-cooled connector helps keep handle temperatures stable and cable weight manageable during long sessions.     GlossaryContactor: high-power relay that connects the main circuitDuty cycle: percentage of time the control signal is on within one cycleInsulation check: verification that high-voltage parts are not leaking to groundPlug and Charge (ISO 15118): certificate-based automatic authentication over the same cable     FAQs Can I just plug in and start?Some vehicles support Plug and Charge (ISO 15118) for certificate-based automatic authentication. Otherwise use RFID or the operator’s app.   Why did my session fail to start?Press until the latch clicks, check the cable route (no sharp bends), clean visible dirt on the connector, then try the app if RFID times out.   Why does charging sometimes slow down?Stations and vehicles reduce current near high state-of-charge, when the connector warms up, or when the site balances power across stalls.   What exactly is being billed?Energy in kilowatt-hours forms the base. Operators may add time-based or session fees and taxes; the receipt lists the components.