Onboard Charger

An onboard charger is the device inside an electric car that converts AC power from a Level 1 or Level 2 charger into DC power for the battery. Its rating sets the car's maximum AC charging speed.

A wall charger offers power, and the onboard charger decides how much to take. If a car's onboard charger were rated at 7.7 kW, a 48 amp wall unit capable of 11.5 kW would still charge it at 7.7 kW. The guide to home EV charger sizes shows how to match the two.

DC fast charging skips the onboard charger, since the station does the conversion. In the EV charging time calculator, use the smaller of the charger and onboard charger ratings. The EV charging time formula guide covers this step.