Short answer: A communication signal between the charger and car that negotiates charging parameters and ensures safety before power flows.
Explanation
The pilot signal, formally called the Control Pilot (CP), is a small electrical signal that runs through a dedicated pin in the charging connector. It serves as the primary communication channel between the charger and the car during AC charging. The signal tells the car how much current the charger can provide, and the car tells the charger it is ready to receive power.
Before any power flows, the pilot signal goes through several states. First it confirms a car is physically connected. Then the car signals its readiness. The charger responds with the maximum current available. Only when both sides agree does power flow begin. If the pilot signal is lost at any point during charging, the session stops immediately as a safety measure.
Pilot signal issues are a common cause of charging failures. A dirty or damaged connector pin, a loose cable connection, or a software glitch can disrupt the signal. If your charger repeatedly fails to start, especially at a specific charger or with a specific cable, a pilot signal problem might be the cause.
Where you'll see this
- On the charger screen
Common confusion
The pilot signal is not the same as ISO 15118 communication. The pilot signal is a simpler analog signal used for basic AC charging negotiation. ISO 15118 adds a digital communication layer on top for features like Plug & Charge.
Example
A charger that repeatedly shows 'communication error' or 'vehicle not detected' despite the cable being firmly connected may have a pilot signal issue, either in the charger's cable or the car's charge port.
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