How EV Charging Actually Works: Step-by-Step
How EV Charging Actually Works
The full sequence
You plug in
The cable is inserted into both the charge point and the vehicle. On chargers with a locking socket or tethered cable, a physical or motorised lock engages to hold the connection securely in place for the duration of charging.
Charger detects the cable
The charger detects that a cable is present and properly connected, via a dedicated signal built into the connector (the "control pilot" line, part of the international charging standard). Nothing is live yet at this point beyond the low-voltage signalling circuit.
Car and charger "talk" to each other
Using that same control pilot signal, the charger and vehicle exchange information — the charger communicates the maximum current it can safely supply, and the vehicle confirms it's ready to charge. This happens automatically in a fraction of a second, with no input needed from the driver.
Safety checks happen
Before any real current flows, the system verifies the connection is genuinely secure, checks for any earth or insulation faults, and confirms the vehicle is correctly connected — not just present, but properly locked and communicating correctly.
Charger asks for power, contactor closes
Once every check has passed, the charger's contactor (a large relay-like switch) physically closes, connecting the vehicle to the mains supply for the first time in the sequence. This is the point where you'll typically hear a single audible click.
Charging begins, managed by the vehicle
The vehicle's own battery management system takes over from here, controlling exactly how much current it draws (up to the maximum the charger offered) based on battery temperature, current charge level, and any charge limit you've set. The charger doesn't push power at the car — the car pulls what it needs, within the ceiling the charger allows.
Continuous monitoring throughout
For the entire session, both the charger and vehicle continuously monitor the connection and current flow, ready to interrupt the session immediately if a fault, disconnection, or unsafe condition is detected. This is also where features like dynamic load balancing operate, adjusting available current in real time based on the rest of the property's electricity usage.
Session ends
Charging stops either when the battery reaches its target charge level, the scheduled charging window ends, or the driver manually stops the session. The contactor opens, disconnecting power, and the cable can then be safely unlocked and removed.
Why this design matters
Understanding this sequence explains a lot of behaviour that otherwise looks confusing. The connector's pins aren't live until deep into this process, which is why charging in the rain is safe. The vehicle — not the charger — makes the final call on current draw, which is why charging speed depends on so many factors. And continuous monitoring throughout the session is why a charger can trip mid-session rather than only failing at the start.
AC vs DC charging — a quick note
Everything above describes AC (Mode 3) charging, which is how virtually all home and destination charge points work — the vehicle's onboard charger converts AC from the wall into DC to store in the battery. DC rapid and ultra-rapid public chargers work differently: they convert AC to DC before it reaches the car, bypassing the vehicle's onboard charger entirely and allowing much higher charging rates, subject to the vehicle's separate DC charging limit.
Frequently Asked Questions
Does the charger control how fast my car charges?
The charger sets an upper limit on the current available, but the vehicle's own battery management system decides how much of that it actually draws, based on factors like battery temperature and charge level. The car pulls power within the ceiling the charger offers, rather than the charger pushing a fixed amount at the car.
What is the "control pilot" signal?
The control pilot is the low-voltage signalling connection within the Type 2 (or Type 1) connector that allows the charger and vehicle to communicate before and during charging — detecting connection, negotiating available current, and monitoring for faults throughout the session. It's separate from the main power-carrying pins.
Why does my charger click when charging starts?
That's the contactor, the internal switch that physically connects the vehicle to the mains supply, closing once all the safety checks have passed. A single click at the start and end of a session is completely normal — repeated clicking during a session is different and usually points to load balancing or a contactor fault.
What is the difference between AC and DC charging?
AC charging (used by virtually all home chargers) relies on the vehicle's own onboard charger to convert incoming AC power to DC for the battery, which limits its maximum speed. DC charging (used by public rapid/ultra-rapid chargers) converts power to DC before it reaches the car, bypassing the onboard charger and enabling much higher charging rates.