The Fundamental Difference
The electricity supplied by the grid is alternating current (AC). EV batteries store direct current (DC). This means AC power must be converted to DC before it can be stored in the battery. The key difference between AC and DC charging is where this conversion happens. In AC charging, the conversion happens inside the vehicle using its onboard charger (OBC). In DC charging, the conversion happens in the external charging unit, and DC power is delivered directly to the battery.
AC Charging: How It Works
In AC charging, the charger supplies AC power to the vehicle. The vehicle's onboard charger (OBC) converts this AC power to DC and manages the charging process. The maximum charging speed is limited by the OBC capacity — typically 7 kW, 11 kW or 22 kW depending on the vehicle. AC charging is the standard method for home and workplace charging, and is used at most public charging points.
- Power range: 3.7 kW (single-phase 16A) to 22 kW (three-phase 32A)
- Conversion: inside the vehicle (onboard charger)
- Infrastructure: relatively simple — wallbox or charging post
- Cost: lower infrastructure cost than DC
- Typical use: home, workplace, depot overnight charging, public parking
DC Charging: How It Works
In DC charging, the charging unit contains the AC-to-DC conversion equipment. DC power is delivered directly to the vehicle's battery, bypassing the onboard charger. This allows much higher power levels — from 50 kW to 720 kW — enabling significantly faster charging. DC charging requires more complex and expensive infrastructure but is essential for rapid charging applications.
- Power range: 50 kW to 720 kW (and beyond)
- Conversion: inside the charging unit (external)
- Infrastructure: complex — requires significant electrical infrastructure
- Cost: significantly higher than AC infrastructure
- Typical use: motorway charging, commercial hubs, rapid turnaround operations
Comparison: AC vs DC
The choice between AC and DC charging depends on the application, required charging speed and available budget.
| Factor | AC Charging | DC Charging |
|---|---|---|
| Power range | 3.7–22 kW | 50–720 kW |
| Conversion location | Inside vehicle (OBC) | Inside charger |
| Speed limitation | Vehicle OBC capacity | Charger power output |
| Infrastructure cost | Low–moderate | High–very high |
| Installation complexity | Low | High |
| Typical charge time (60 kWh) | 3–16 hours | 8–75 minutes |
| Best use case | Overnight, depot, workplace | Rapid top-up, commercial hubs |
| Battery impact | Lower stress | Higher stress (heat) |
When to Use AC Charging
AC charging is the right choice for most routine charging needs. If a vehicle has sufficient time to charge — overnight at home, during a working day at a workplace, or overnight at a depot — AC charging is more cost-effective, gentler on the battery and simpler to install. For fleet operators with predictable overnight dwell times, AC depot charging is typically the primary charging method.
When to Use DC Charging
DC fast charging is appropriate when vehicles need to be recharged quickly — during operations, at motorway stops on long journeys, or at commercial hubs with high vehicle throughput. For fleet operations where vehicles cannot be taken out of service for extended periods, DC charging enables rapid turnaround. Ultra-fast DC charging (150 kW+) is increasingly deployed at motorway service areas and commercial charging hubs.
WOX Charging Solutions
WOX provides a complete range of charging infrastructure from 7 kW AC wallboxes to 720 kW ultra-fast DC terminals. All WOX chargers support OCPP 2.0.1 for cloud management, load balancing and smart charging integration. WOX charging solutions are designed for home, fleet depot, commercial and public applications.
Key Takeaways
- 1AC charging converts power inside the vehicle — limited to 7–22 kW
- 2DC charging converts power externally — enables 50–720 kW speeds
- 3AC is ideal for overnight and depot charging — lower cost, gentler on batteries
- 4DC is for rapid turnaround and long-distance travel
- 5Most fleet operations use AC as primary, DC as supplementary
Summary
AC charging converts power inside the vehicle and is limited to 7–22 kW by the onboard charger — ideal for overnight home, workplace and depot charging. DC charging converts power externally and delivers up to 720 kW directly to the battery — essential for rapid turnaround and long-distance travel. Most fleet operations use AC as the primary charging method, with DC for operational top-ups.