CCS Signaling CP function

The signaling protocol has been designed for the following charging sequence.

• supply equipment signals presence of AC input power

• vehicle detects plug via proximity circuit (thus the vehicle can prevent driving away while connected) and can detect when latch is pressed in preparation for plug removal.

• Control Pilot (CP) functions begin

• supply equipment detects plug-in electric vehicle (PEV)

• supply equipment indicates to PEV readiness to supply current

• PEV ventilation requirements are determined

• supply equipment current capacity provided to PEV

• PEV commands energy flow

• PEV and supply equipment continuously monitor continuity of safety ground

• charge continues as determined by PEV

• charge may be interrupted by disconnecting the plug from the vehicle

The technical specification was described first in the 2001 version of SAE J1772 and subsequently the IEC 61851-1 and IEC TS 62763:2013. The charging station puts 12 V on the Control Pilot (CP) and the Proximity Pilot (AKA Plug Present: PP) measuring the voltage differences. This protocol does not require integrated circuits, which would be required for other charging protocols, making the SAE J1772 robust and operable through a temperature range of −40 °C to +85 °C

Control Pilot (Mode): The charging station sends a 1 kHz square wave on the control pilot that is connected back to the protective earth on the vehicle side by means of a resistor and a diode (voltage range ±12.0±0.4 V). The live wires of public charging stations are always dead if the CP–PE (Protective Earth) circuit is open, although the standard allows a charging current as in Mode 1 (maximum 16 A). If the circuit is closed, the charging station can also verify that the protective earth is functional. The vehicle can request a certain charging function by setting the resistance between the CP and PE pins; 2.7 kΩ announces a Mode 3 compatible vehicle (vehicle detected) which does not require charging. 880 Ω says the vehicle is ready to be charged, and 240 Ω requests with ventilation charging, in which case the charging stations supplies charging power only if the area is ventilated (i.e., outdoors).

The Control Pilot line circuitry examples in SAE J1772:2001 show that the current loop CP–PE is connected permanently on the vehicle side via a 2.74 kΩ resistor, making for a voltage drop from +12 V to +9 V when a cable is hooked up to the charging station, which activates the wave generator. The charging is activated by the vehicle by adding parallel 1.3 kΩ resistor resulting in a voltage drop to +6 V or by adding a parallel 270 Ω resistor for a required ventilation resulting in a voltage drop to +3 V. Hence the charging station can react by only checking the voltage range present on the CP–PE loop. Note that the diode will only make for a voltage drop in the positive range; any negative voltage on the CP–PE loop is blocked by D1 in the vehicle, any significant current that does flow in the CP–PE loop during the negative period will shut off the current as being considered a fatal error (like touching the pins).

For IEC62196-2 male plugs the Control Pilot pin is made shorter to prevent untethered cables being used as "extension leads", This prevents the use of downstream cables that may have a lower current capability being connected to a cable of a higher current rating.

Control Pilot (Current limit): The charging station can use the wave signal to describe the maximum current that is available via the charging station with the help of pulse-width modulation: a 16% PWM is a 10 A maximum, a 25% PWM is a 16 A maximum, a 50% PWM is a 32 A maximum and a 90% PWM flags a fast charge option.

The PWM duty cycle of the 1 kHz CP signal indicates the maximum allowed mains current. According to the SAE it includes socket outlet, cable and vehicle inlet. In the US, the definition of the ampacity (ampere capacity, or current capacity) is split for continuous and short term operation. The SAE defines the ampacity value to be derived by a formula based on the 1 ms full cycle (of the 1 kHz signal) with the maximum continuous ampere rating being 0.6 A per 10 µs up to 850 µs (with the lowest (100 µs/10 µs) × 0.6 A = 6 A). Above 850 µs, the formula requires subtraction of 640 µs and multiplying the difference by 2.5. For example ((960 µs − 640 µs)/10 µs) × 2.5 A = 80 A.