How DC Charging Works
There are a few different ways to charge your EV. Understanding the difference is key to choosing the right option for your needs. From slower AC charging at home or work to much faster DC charging at public rapid and ultra-rapid stations, each method plays a different role in day-to-day EV driving.
In this blog, Pro EV looks at what DC charging is, how it works, and how it compares with other EV charging options.
Whether you’re new to electric vehicles or just want to know more about how public charging works, we’ve provided you with the essentials in this guide to help you feel more confident about charging your EV efficiently and effectively.
What Is DC Charging?
DC charging, or direct current charging, is one of the quickest ways to charge an electric vehicle. Instead of sending power through the car’s onboard charger first, DC charging delivers electricity straight to the battery, which helps speed up the process.
That is why DC charging is often used at public rapid charging stations when drivers need to recharge quickly.
You will usually find DC chargers at places like motorway service stations, charging hubs, and some retail parks. They are especially useful for longer journeys, quick stop-offs, or for drivers who do not always have time to charge at home.
It is also worth knowing that not every electric vehicle charges at the same speed. The charging rate can depend on the car itself, the charger being used, and how full the battery already is. In most cases, DC charging works fastest when the battery is at a lower level, then gradually slows as it approaches full.
What’s the Difference Between AC and DC Charging?
When charging an electric vehicle, you will usually encounter two main charging types: AC and DC. Although they’re both used to recharge an EV battery, they work in slightly different ways and are designed for different charging situations.
AC charging stands for alternating current. When you plug into an AC charger, the electricity has to be converted inside the car by the vehicle’s onboard charger before it can be stored in the battery.
DC charging stands for direct current. With this type of charging, the electricity is converted before it reaches the car, inside the charging unit itself.
So, what are the key differences between the two?
- Speed: AC charging is usually slower, while DC charging is much faster.
- Where it is used: AC charging is common at home, at work, and on slower public chargers. DC charging is mostly found at public rapid and ultra-rapid charging points.
- Best for: AC charging is best for overnight or everyday charging, but DC charging is better for quick top-ups and longer journeys.
- Charging cost: AC charging, especially at home, is often more affordable. DC charging tends to cost more because it offers higher charging speeds.
- Convenience: AC charging works best for routine charging when the car can be left plugged in for longer. DC charging is more useful when you need to get back on the road quickly.
In simple terms, AC charging is usually the better option for regular day-to-day charging, while DC charging is designed for speed and convenience when time matters most.
How DC Fast Charging Works
DC fast charging is designed to charge electric vehicles much more quickly than standard charging methods. But how does it do this?
Instead of sending power through the car’s onboard charger, a DC fast charger converts the electricity before it reaches the vehicle and then delivers it straight to the battery, making it a much speedier process.
When you plug an EV into a DC fast-charging station, the charger and the car begin communicating immediately. Before charging, the vehicle’s battery management system checks things like:
- Battery temperature,
- Current charge level
- How much power the car can safely accept.
The charger will then adjust the flow of electricity to match your vehicle’s needs, helping charge the battery as quickly and safely as possible.
What Affects DC Charging Speed?
Although DC fast charging is considered one of the quickest ways to charge an EV, charging speeds are not always consistent.
Several factors can affect DC charging speed, including the power the charger can deliver, the power the car can accept, and the battery’s condition at the time of charging. Pro EV’s guide to kW vs kWh EV charging terms explains the difference between charger output and battery capacity and why both matter.
Some of the key factors that affect DC charging speed are:
- The charger’s power output – A 50kW charger will usually charge slower than a 150kW or 350kW unit. Although the vehicle must also be able to accept that level of power.
- The car’s maximum charging speed – As mentioned above, every EV has its own limit for DC fast charging, so a higher-powered charger won’t always result in a faster session.
- Current battery level – Charging is typically quickest when the battery is at a lower state of charge and slows down as it approaches full.
- Battery temperature – If the battery is too cold or too hot, the vehicle may reduce charging speed to protect the battery and maintain efficiency.
- Battery size and condition – Larger batteries can often endure stronger charging speeds for longer. Battery age and condition can also influence performance.
- Charging conditions and charger availability – At some public places, charging speed can vary depending on network conditions or whether power is being shared between multiple EVs.
To put it simply, how fast DC charging works for your EV depends on a mix of charger capability, vehicle compatibility, and battery conditions.
Still have questions?
Frequently Asked Questions
Why does DC charging slow down as the battery fills up?
Charging is usually fastest when the battery is at a lower charge level. As the battery reaches full capacity, your EV reduces the charging rate to protect battery health and manage heat more effectively. This is why many drivers use DC fast charging for a quick top-up rather than charging all the way to 100 per cent.
How long does DC fast charging take?
That depends on the battery size, the charger’s power, and the vehicle’s maximum charging rate. Take a look at our guide on how long it takes to charge an electric car.
Can all electric cars use DC fast charging?
Not all EVs can use DC fast charging. In the ones that can, the maximum charging speed can vary a lot. Some EVs are designed to sustain much higher charging rates than others, which is why it’s crucial to remember that the same rapid charger may give different results depending on the car.
Is DC charging bad for the battery?
Occasional DC fast charging is a normal part of EV ownership and has proved very useful, especially for longer trips. It’s best to use a mix of home charging and public rapid charging to balance convenience and battery care.
