AC vs. DC EV Charging: What are the Differences?⚡Australia

HOW DOES AC ELECTRIC VEHICLE CHARGING WORK?

In Australia, all home and home appliances run on grid-supplied alternating current (AC) electricity. Because of this, most residential EV chargers run on AC, and can provide from 7kW to 22kW of charging power to the EV.

How fast is AC EV Charging? AC charging consists of level 1 and 2 chargers, providing from 2.4kW in a standard home outlet, 7kW for single phase, and up to 22kW for three-phase properties using three-phase electric vehicle chargers like myenergi’s Zappi charger.

Whilst AC chargers can provide up to 22kW of charging, it’s important to note that your EVs built-in inverter (or ‘on-board charger’) may bottleneck charging speeds with specification limitations.

What does alternating current mean? Compared to DC power, AC is what households and their appliances run on. AC runs completely different to how DC operates, which means that electricity is converted between both depending on the load its powering or its transmission.

WHAT IS AN ELECTRIC VEHICLES 'ON-BOARD CHARGER'?

An onboard EV charger or inverter is responsible for converting chargers’ AC electricity from the home or grid to DC electricity for the battery. The onboard charger is only required for AC chargers and can be a limitation to charging speeds depending on your EV model.

For example, the Tesla Model Y has an 11kW on-board charger which works well with Tesla Wall Connector which provides up to 11.5kW of AC charging power, but also means that a 22kW charger won’t be fully utilised as the inverter is capped at 11kW.

Is 11kW three-phase? As single-phase properties can only get 7kW, to achieve 11kW your property will need to be three phase.

HOW DOES DC ELECTRIC VEHICLE CHARGING WORK?

Unlike AC power, DC power doesn't need to be converted as your EV's battery also runs on DC power. This removes the need for conversion from the charger to the EV's battery.

By being able to bypass the on-board inverter/charger and its bottlenecking limitations, the EV can be charged at much higher rates (up to almost 500kW), as it directly feeds the battery.

DC fast chargers (DCFC) are typically used in applications like public and fleet EV charging stations that require fast and rapid charging systems to recharge electric vehicles as quickly as possible. These are typically very expensive to install, but also enable public charging capability.

What does direct current mean? Elements like solar, battery storage, and your EV all run on DC power. DC operates differently to how AC does as the current only travels in one direction rather than alternating.

SHOULD I BE USING AC OR DC CHARGING?

In most cases, a combination of both AC and DC charging will be sufficient in keeping your electric vehicle topped up. However, there may be situations where certain drivers have specific requirements that may alter recommendations.

For example, if you’re someone who works all day, and then parks in their garage at night and repeats the next day, an AC EV charger may be preferential as it fits directly into your lifestyle.

On the other hand, if you’re someone who is regularly on the road and needs constant 0-80% charges as quickly as possible, relying on public DC chargers may be the better choice.

Most EV owners will opt for both solutions, with AC charging being much more convenient at home, and relying on public EV charging stations for quick charges throughout the week.

IS AC OR DC CHARGING BETTER FOR EV BATTERY LIFESPANS?

Because both AC and DC chargers technically end up charging the battery with DC electricity with either the DC charger or on-board charger supply the DC electricity, it shows us that AC and DC don’t directly affect the battery’s lifespan.

The battery lifespan is determined by the speed of the charging. AC chargers max out at 22kW which is a good speed for gradual and consistent charging, whilst DC chargers can reach up to 480kW. High-powered chargers provide generate more heat and cell stress, but with modern charging management technology, the difference is minimal.

During the process of fast charging, the curve is set to optimise battery performance and prolong battery health to ensure longevity.

Courtesy of Erik Mclean on Pexels.

AC electric vehicle chargers generate heat like other electronics, however, they are designed to have adequate cooling by implementing natural convection or passive cooling. Fans aren’t required because the charger is not inverting the AC to DC which would generate heat from conversion power loss.

DC EV charging stations require strong cooling methods to deal with the high-power transfer and inversions that happen inside the charger unit. Delivering hundreds of kW of power at any given time, DC superchargers require heat management like liquid cooling in the charger, and sometimes in the charging cable itself.