On-Board Charger (OBC)
The on-board charger (OBC) is a component built into the EV that converts alternating current (AC) from the electrical grid into direct current (DC) that the battery can store. Its power rating determines the maximum AC charging speed.
How It Works
When you plug an EV into a home outlet, workplace charger, or public AC charging station, the electricity arrives as AC. The battery can only store DC, so the on-board charger performs the AC-to-DC conversion inside the vehicle.
The on-board charger's power rating — measured in kW — is the bottleneck for AC charging speed. Even if you connect to a 22 kW AC charging station, a vehicle with an 11 kW on-board charger can only charge at 11 kW.
DC fast chargers bypass the on-board charger entirely by converting AC to DC in the charging station and feeding DC directly to the battery — which is why DC charging can achieve much higher power levels.
Why It Matters
The on-board charger rating directly affects overnight and workplace charging times. A vehicle with a 22 kW on-board charger can fully charge a 77 kWh battery in about 3.5 hours on a 22 kW AC station. The same battery with an 11 kW charger takes about 7 hours — still overnight-friendly, but more constrained for daytime top-ups.
For buyers who rely primarily on home charging with a dedicated wallbox, the on-board charger rating determines how quickly the car recovers range overnight.
Common Values
- Budget/standard: 7.4 kW (single-phase)
- Mid-range: 11 kW (three-phase)
- Premium: 22 kW (three-phase)
- Single-phase home: limited to ~7.4 kW regardless of OBC
- Three-phase home (common in Europe): can utilize 11 kW or 22 kW OBC