What is an AC and DC charger?

What’s the Difference Between AC and DC?

Most charging stations you’ll find today use AC charging. The usual charging speed is 22 kW, depending on the car you own and the power available to the charging infrastructure. It’s ideal for charging your car at home or work because you’ll need more time to load. DC charging, however, is more common near highways or at public charging stations, where you need quick recharges. But DC charging is making its way into home charging, offering new possibilities as it not only fast-tracks charging but also supports bidirectional charging.

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EV Charging: The Difference Between AC and DC

Last updated on April 14, 2023

When it comes to electric mobility, two types of electrical currents can be used to charge an electric vehicle (EV)—AC (alternating current) and DC (direct current).

All home EV chargers and the majority of public charging stations use AC, while DC is used for fast charging.

When we talk about charging an EV, the main difference between AC and DC charging (and the time it takes to do so) is where the conversion from AC to DC happens, i.e., in the vehicle or the charging station.

• The power that comes from the grid is always AC (alternating current).
• The energy stored in batteries is always DC (direct current).

This article explores the differences between AC and DC EV charging and looks at how it works.

The EV Charging Ecosystem

Electric mobility is more popular than ever, and growing alongside it is the EV charging ecosystem. On paper, the concept is simple: instead of filling up a tank with fuel at gas stations, EVs plug into a charging station to top up their batteries.

In practice, however, not all chargers are created equal. EV charging stations come in various shapes, sizes, and use cases. One main factor that differentiates them is the type of current they use.

Difference Between AC and DC

Before getting technical, 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 stored in batteries is always DC (direct current).

AC and DC are two entirely different types of electrical currents. They travel in different directions, flow at varying speeds, and have different applications. The band AC/DC, despite their name, has nothing to do with electrical currents or EV charging.

AC 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—hence why virtually all of the world’s electricity grids use AC power, and why you find AC power flowing from the sockets in your home and office.

DC Charging

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, powering electronics, and LED lighting. Batteries store DC power, and though you may not realize it, every time you charge your laptop, the charger converts 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.

What Is the Difference Between AC and DC Charging?

For more information, please visit Ac and Dc Charger.

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 car’s battery will always 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 to the battery. Because the conversion process happens inside the more spacious charging station and not the EV, more powerful converters can be used to convert AC from the grid quickly. As a result, some DC stations can provide up to 400 kW of power and fully charge an EV in minutes.

Myth debunked: DC charging isn’t bad for your battery, contrary to common belief.

EV Charging Curves

Another key difference between AC and DC charging is how their power output fluctuates over the course of a charging session, known as the EV charging curve.

AC Charging Curve

With AC charging, the power flowing to an EV represents a flat line, meaning not much of a curve at all. This is due to the relatively small onboard converter that can only handle a limited power spread over longer periods.

DC Charging Curve

By bypassing the car’s slower onboard converter, DC charging can deliver much higher power, but its output forms a decreasing charging curve. This is because the EV's battery initially accepts a high flow of power but gradually takes in 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 need to slow down as you get to the top, so the glass doesn’t overflow.

This same logic applies to DC fast and ultra-fast charging. This is why EVs require less power once the battery is around 80 percent full, resulting in the decreasing power output observed.

Charging speed and power can vary based on several factors. For more on what influences EV charging times, see our in-depth article.

AC vs. DC Charging

By now, you probably understand that AC and DC charging work quite differently and serve different roles. You might think that since DC charging is faster, it should always be your preferred option.

While DC charging is fast, it also relies on more bulky and expensive equipment and requires a high-voltage connection to the power grid, making it impossible to install at home. Due to this high upfront cost, DC charging station operators generally pass this cost to you by setting higher prices compared to AC chargers. Even the slowest dedicated AC charging station can fill a medium-sized EV overnight, so you probably won’t need DC charging for your daily travels.

Where DC charging shines is for quick top-ups on long trips. Depending on your car’s charging capacity and the station’s power output, a DC charger can power up your EV in under an hour, allowing you to quickly resume your journey.

Want to Learn More About EV Charging?

Understanding the type of current used by a charging station is essential, but there are many more facets to EV charging, including where to find EV chargers, how to use them, and how to pay for them. If you're looking to learn more about EV charging or have just bought your first electric car, check out our detailed guide for a comprehensive overview.

Contact us to discuss your requirements for a Charging Pile. Our experienced sales team can help identify options that best suit your needs.