What is the difference between AC and DC Charging?

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The national grid delivers AC (Alternating Current) but Electric Vehicles must charge their batteries with DC (Direct Current).

An AC charging point/EVSE supplies the vehicle’s onboard charger which in turn converts the AC power to DC allowing the battery to be charged. The size of the onboard charging device is constrained by the space inside the vehicle and price point the manufacturer needs to sell the car. Because the onboard converter is small, the amount of power that they are able to deliver to the battery is typically low (3-6kW).

A DC fast charger bypasses the onboard charging device, supplying power directly and safely to the vehicle’s battery. The DC charger is external to the vehicle and therefore not constrained in size or cost. DC fast chargers use 3-phase power, and have smart technology, enabling them to adjust the charge level to suit the battery state.

 

AC vs DC diagram