AC Charging
Why a 22 kW Charger Only Charges Your Car at 11 kW
The onboard charger, the phases and the cable limit AC charging speed. Why a 22 kW wallbox gives 7.4 or 11 kW and how to check what your car accepts.
- Prepared by
- VULTAE Engineering Team
- Published
- Reading time
- 1 min
- Sources
- —
Key takeaways
- 1AC charging speed is limited by the car’s onboard charger, not only by the wallbox. A car with an 11 kW onboard charger will not charge faster than 11 kW even on a 22 kW wallbox.
- 2Single-phase cars are limited by one phase, usually up to 7.4 kW at 32 A. Three-phase cars can use more, up to the onboard charger limit.
- 3Before buying a 22 kW charger, check the vehicles’ onboard charger rating and phases. Often 11 kW is enough and the supply cost is lower.
Short answer: the car sets the limit. The charger offers up to its rated power, the car’s onboard charger accepts what it can. A 22 kW wallbox charging a car with an 11 kW onboard charger delivers 11 kW.
What limits AC charging speed
| Limit | Example |
|---|---|
| Wallbox rating | 22 kW three-phase |
| Supply | Breaker and cable may be smaller |
| Cable rating | 16 A or 32 A |
| Car’s onboard charger | 7.4, 11 or 22 kW |
| Phases the car uses | 1 or 3 |
The slowest link decides.
Examples
| Car onboard charger | On a 22 kW wallbox | Result |
|---|---|---|
| 3.7 kW single-phase | 22 kW | 3.7 kW |
| 7.4 kW single-phase | 22 kW | 7.4 kW |
| 11 kW three-phase | 22 kW | 11 kW |
| 22 kW three-phase | 22 kW | 22 kW |
How to check
- Find the maximum AC charging power in the vehicle specification.
- Check whether the car uses one or three phases.
- Check the wallbox current setting and supply.
- Look at the charging power reading on the car or app.
What this means for buying
| Situation | Choice |
|---|---|
| All cars 11 kW or less | 11 kW wallbox |
| Mixed fleet including 22 kW cars | 22 kW if the supply allows |
| Single-phase supply | 7.4 kW |
Use the charging time calculator to compare, and see 22 kW chargers and single vs three phase. VULTAE’s smart wallbox comes in 3.7, 7.4, 11 and 22 kW.
Questions buyers ask
- Why is my 22 kW charger giving 11 kW?
- The car’s onboard charger accepts only 11 kW, or the car is single-phase, or the supply or settings limit the current. Check the vehicle specification and the charger settings.
- Which cars accept 22 kW AC?
- Only some models. Check the vehicle manual or specification for its maximum AC charging power and phases.
- Is a 22 kW wallbox a waste?
- Not if a mixed fleet or future cars can use it, but it costs more to supply. Many sites choose 11 kW and save on cable and supply.
