Both of them — and the answer flips with the charging type. On AC charging, the charger announces a ceiling and the car decides how much to draw beneath it, so the car is the decider and the charger is the referee. On DC fast charging the direction reverses: the car continuously asks for the voltage and current it wants, and the charger delivers what it can within its own rating. That flip explains most confusion about charging speeds.
Key Takeaways
- On AC, the charger sets a ceiling and the car decides the draw — the car is the decider.
- On DC, the car requests and the charger delivers within its rating — the direction flips.
- A charger’s headline figure is a capability, never a promise to a specific car.
- Adjustable settings move the AC ceiling; they never move the deciding role.
On AC: the Charger Offers, the Car Decides
An AC charger does not convert power for the battery. It is a supervised supply point: it states, on the pilot signal, the maximum current available — set by the unit, its setting and the circuit behind it (sized as a continuous load, breaker at 125% of charger current under the National Electrical Code). The car’s onboard charger does the converting and drawing, never above the advertised ceiling or its own limit. The summary in how home EV chargers work shows where that unit sits in the chain.
| AC ceiling | Set by | Result |
|---|---|---|
| The advertised offer | The charger, its setting and its circuit | The highest current any car may take at this point |
| The car’s onboard limit | The car maker | A car with a smaller onboard charger stops here, whatever the wallbox offers |
| The session draw | The car, moment by moment | At or below both ceilings — the car can always choose less |
On DC: the Car Asks, the Charger Delivers
A DC fast charger does the converting itself, so the relationship inverts. The battery’s state — its charge level, temperature and design limits — decides what it can accept, and the car passes that request to the charger over the digital conversation that CCS builds on the J1772 foundation. The charger then supplies what was asked, up to its own rated capability. This is why DC speed rises and falls with the battery’s condition instead of holding at the headline figure: the request, not the offer, is in charge. The charger remains the safety referee — insulation checks, connection monitoring, an instant stop on any fault — but it does not set the pace.
Why the Answer Matters When You Shop
- A 48 A wallbox cannot push 48 A into a car whose onboard charger accepts less — buying above your car’s limit buys headroom for a future car, not speed for this one.
- A DC charger’s rated kilowatts are a capability ceiling, not a promise to every car. Your car’s requests decide the session, so two cars at the same DC charger can charge at very different speeds.
- An adjustable AC charger changes the offer, not the decider. Lowering the setting lowers the ceiling; the car still chooses everything beneath it.
- Mode labels tell you which conversation you are in — the modes in Mode 2 vs Mode 3 charging are AC conversations; DC is the requesting kind.
The Two Decision Models in the EVDANCE Range
The EV-ACT5006T wall charger (up to 48 A, NACS, IP65/IP66) is the AC model: it publishes a ceiling, and every car that plugs in takes what its onboard charger decides — which is why the same wallbox serves a small hatchback and a large SUV at different speeds. The EV-RHDC30K-L compact DC charger (22 kW DC, OCPP 1.6J, IP54) is the DC model: it delivers within its rating what each car requests, so the pace belongs to the car’s battery, not the badge.
Frequently Asked Questions
Can a charger force too much current into a car?
No. On AC the car draws — a charger cannot push current into a car that is not taking it. On DC the car requests — the charger follows the request within its rating. Both directions are bounded by the lower of the two sides.
Why does my car charge slower than my wallbox’s label?
Because on AC the label is the offer, and your car’s onboard charger is the decider. If its limit is below the wallbox’s ceiling, the car’s figure is your speed — the wallbox is not underperforming.
Who decides on a public DC charger — is it the network?
The network sets prices, access and sometimes a site power cap, but the moment-by-moment current is still the car’s request answered by the charger. A cap lowers the ceiling; it does not take over the asking.
Related Reading
- How Do Home EV Chargers Work?
- Does J1772 Work With CCS? CCS Connectors Explained
- Mode 2 vs Mode 3 Charging: What IEC 61851 Means for Portable EV Chargers
- What Is J1772? The North American EV Plug Explained
