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EV charging: the difference between AC and DC

When it comes to electric mobility, two separate electrical currents can be used to fuel an electric vehicle (EV)—AC (alternating current) and DC (direct current). But, before we dive in, there are two things you should keep in mind:

The power that comes from the grid, i.e., your domestic socket, is always AC (alternating current).

The energy that is stored in batteries is always DC (direct current).

AC and DC, not AC/DC

AC and DC are two entirely different types of electrical current. Both travel in different directions, flow at different speeds, and have different applications. AC/DC are a hard rock band that, despite having an album titled “High Voltage,” have nothing to do with electrical currents or EV charging.

AC is an electrical current, or flow of charge, that periodically changes direction, i.e., it alternates. AC power can be generated from renewable sources that use rotating generators, such as wind or hydropower turbines. AC can also be efficiently transported over long distances—which is why virtually all of the world’s electricity grids use AC power, and why you can find AC power in your home and office.

DC always moves in a straight line and can be generated by renewable power technologies such as solar panels. Among other things, DC can be used for energy storage and LED lighting. Batteries store DC power, and though you may have never realized it, every time you charge your laptop, the charger converts the AC power from the grid into DC power for your laptop’s battery.

In short, we get AC power from the grid and this is converted into DC power so it can be stored in batteries, such as the one used to power an EV.

AC and DC charging in electric mobility

When we talk about charging an EV, the main difference between AC and DC charging is where the conversion from AC to DC happens. No matter whether an EV uses an AC or DC charging station, the EV’s battery will still only store DC energy.

When you use a DC charging station, the conversion from AC (from the grid) to DC happens within the charging station—allowing DC power to flow directly from the station and into the battery. Because the conversion process happens inside the more spacious charging station and not the EV, larger converters can be used to convert AC power from the grid very quickly. As a result, some DC stations can provide up to 350 kW of power and fully charge an EV in 15 minutes.

Staying ahead of the curve

Another key difference between AC and DC charging is the charging curve. With AC wallbox ev charger, the power flowing to an EV represents a flat line (so, not much of a curve at all). This is due to the relatively small onboard charger that can only receive a limited power spread over longer periods.

DC EV charger, on the other hand, forms a degrading charging curve. This is due to the EV's battery initially accepting a quicker flow of power but gradually asking for less as it reaches full capacity.

As an example, imagine a glass as the EV’s battery, a water bottle as a DC charging station, and the water inside that bottle as the power. At first, you can quickly fill the glass with water, but you’ll need to slow down as you get to the top, so the glass doesn’t overflow.

The same logic can be applied for DC fast and ultra-fast charging. This is why EVs require less power once the battery is around 80 per cent full, hence the degrading curve you see below.

Other factors that can affect charging speeds include:

Battery percentage (state of charge)

State of the EV’s battery

Weather conditions

AC for the grid and DC for the battery

Both AC and DC are important in the electric mobility world. You get AC power from the grid that is then converted to DC so it can be stored in an EV’s battery. When using an AC charging station, the conversion to DC happens inside the EV via an onboard charger, which is often limited. When using DC fast and ultra-fast charging stations, the conversion happens outside of the EV, using a larger converter.

Want to learn more about our AC and DC charging stations?

We provide a range of charging stations as part of our end-to-end electric vehicle charging solutions for businesses around the world. For a complete list of tech specs and use cases, as well as more information, take a look at our EV chargers for every business looking to electrify its operation.

Electric vehicles have lots in common with gasoline-powered cars—room for four-plus passengers, range of several hundred miles, good safety—plus that one big difference: recharging with a plug at versus refueling from a pump. We’ve all pumped gas and know it’s a five- to 10-minute process; we suspect recharging takes longer and we know there are far fewer charging stations than the 125,000 U.S. public gas stations.

Here’s what you need to know about buying, installing and using the right EV charger. The more you know, the clearer it becomes that the unique aspects of EVs aren’t automatic disqualifiers.

Clearing Up the Range-Anxiety Misconception

With a gas-engine car, most owners drive until it’s low on fuel because gas stations are everywhere and gassing up is a quick stop. But empty-to-full charging is not what EV owners do most of the time. They top off every night or two, and as long as the car is charged in the morning, charging time doesn’t matter and range anxiety isn’t an issue for daily driving. Some use public charging, which means you do have to wait on the car. But 80% of charging is done at home, according to the JD Power U.S. Electric Vehicle Experience (EVX) Home Charging Study

Range and charging time may be less of an issue if an EV is the second car. If an EV is the only car, for long summer or holiday trip, owners can do what owners of compact gasoline-powered sedans may do: Rent a midsize or larger SUV for that two-week vacation. Or find a hotel with on-site charging.

For those who charge at home, you need to have the right charging equipment, and the proper electrical supply.

With EV charging, there isn’t a one-size-fits-all solution. Electric vehicles have different charging capabilities and requirements and every owner also has their own driving needs.

Here’s a look at key aspects of choosing the right EV charging accessories, installing it properly and best practices for using EV charging equipment at home.

Do You Need to Buy an EV Charger When One Comes Free?

Every electric car comes standard with a portable EV charger. (This thick cable that plugs into a wall outlet and the car counts as a charger.) However, every manufacturer provides a different unit, with varying levels of charging capabilities. In some cases, the same manufacturer provides different standard charging equipment depending on which of its EV offerings you purchase or lease.

Some of these supplied chargers are powerful and can fully recharge your EV overnight. These are called Level 2 chargers because they need to be plugged into a 240-volt outlet. (Memory aid: for Level 2, think Level 240 volts. Even if that’s not why it’s called Level 2.)

Some standard, EV-maker-supplied chargers plug into a regular 120-volt household outlet and deliver power slowly. These Level 1 chargers are fine for most plug-in hybrids. PHEVs have smaller batteries than battery electric vehicles (BEVs) do. PHEVs have batteries of about 5 to 20 kilowatt-hours (kWh). Pure EVs are more on the order of 60 kWh to 100 kWh.

Is the automaker-supplied charger enough for a BEV? A rule of thumb to follow in determining if the standard charger is enough for your daily charging needs is: Can it fully recharge your EV’s battery overnight? If it can, you probably don’t need to buy another charger. Keep in mind, if the supplied charger is a Level 2, 240-volt unit, then you’ll need to install a 240-volt outlet in your garage, or wherever you plan to charge the vehicle.

E-mobility has reached a tipping point. More than 250 new models of battery electric vehicles (BEV) and plug-in hybrid electric vehicles (PHEV) will be introduced in the next two years alone, and as many as 130 million EVs could be sharing roads the world over by 2030.1 To support these numbers, significantly expanded charging is required—and it will not be cheap. In fact, an estimated $110 billion to $180 billion must be invested from 2020 to 2030 to satisfy global demand for EV charging stations, both in public spaces and within homes.While EV charging stations in private residences are quite common today, on-site commercial charging will need to become a standard building feature in the next ten years to meet consumer demand. Across the three most advanced EV markets—China, the EU-27 plus the United Kingdom, and the United States—charging in residential and commercial buildings is the dominant place for the foreseeable future and will remain key to scaling the industry. Yet without upgrading buildings’ electrical infrastructure, there simply will not be enough accessible EV chargers to satisfy demand. Further complicating matters, EV charging at scale requires careful planning of a building’s electrical-distribution system as well as local electric-grid infrastructure.To make AC integrated EV charger more accessible and affordable, urban planners, building developers, and electrical-equipment suppliers must integrate charging infrastructure into standard building-design plans. In this article, we detail the effects of expanding EV charging on infrastructure planning cycles and adjacent services. Our resulting considerations and recommendations can inform the decision making of four distinct groups of influencers: developers and property owners, urban planners and regulators, grid operators, and electrical-equipment providers.nitial attempts to mass-market EVs in the early 2000s faced technological limitations, particularly limited driving range, and ultimately failed. Today’s EVs have a range of 150 to 300 miles per charge, making them more than sufficient for the 95 percent of vehicle trips that are less than 30 miles.2 Today, the potential bottleneck is deploying charging infrastructure to service the projected density of EVs.