AC Charging

AC charging refers to replenishing an electric vehicle's battery using alternating current drawn directly from the mains electricity supply or a dedicated wallbox. Because the grid delivers power as AC while batteries can only store and discharge direct current, the alternating current must be converted to DC before it can enter the pack. In AC charging this conversion happens inside the car, which is the defining characteristic that distinguishes it from DC rapid charging.

The component responsible is the on-board charger, a power-electronics unit built into the vehicle. It rectifies the incoming AC, regulates the voltage and current, and feeds clean DC to the high-voltage battery under the supervision of the battery management system. Crucially, the on-board charger sets the ceiling on charging speed: even if the supply point can deliver more, the car will only accept what its charger is rated for. Typical on-board chargers handle between 7 kW on a single-phase domestic supply and 11 or 22 kW where three-phase power is available, the latter being more common in continental Europe than in single-phase households.

This makes AC charging inherently slower than DC fast charging, but its modest pace is well matched to the situations in which it is used. Home and workplace charging usually take place over many hours while the car is parked overnight or during a working day, so there is ample time to fill the battery completely from a 7 kW wallbox. For most owners this routine covers the great majority of their charging needs without ever resorting to a public rapid charger.

The slower delivery also brings advantages for the battery itself. Lower charging currents generate less heat and impose gentler electrochemical stress on the cells, which helps to limit long-term degradation. Topping up at home on AC is therefore considered kinder to battery health than habitual high-power DC charging, and it is markedly cheaper, both because domestic electricity costs less than public rapid charging and because installing a wallbox is far less expensive than the substantial grid connection and hardware required for a DC charger.

In Europe the physical connection is almost universally made through the Type 2 connector, which carries either single-phase or three-phase AC and has become the standard socket on the vehicle and the cable. The same inlet often forms part of a combined connector that also accepts DC.

AC charging sits within a broader ecosystem of related concepts: it is enabled by the on-board charger, delivered through the Type 2 connector, commonly described as Level 2 charging in North American terminology, and contrasted with DC fast charging, which bypasses the on-board charger to deliver direct current straight to the pack.