AC, DC Chargers: Their EV Charging Capacities

4 min read
Feb 25, 2018 9:00:00 AM

Don’t let buzzwords dismay you; you don’t have to be an electrician to understand the basics of EV charging.

In this blog post, we compare AC EV Charging and DC EV charging.

  • How do they differ?
  • How are they currently in use?

Private use vs. public use

Home and offices are the most common places to recharge batteries for most EV drivers. While they are convenient and allow for long(er) charging sessions, they aren’t the most effective setups. Here’s why.

The technical explanation

Charging speed isn’t only reliant on the charging station. It also depends on the electric capacity of the infrastructure it’s attached to.

As an example, most private EV charging stations can deliver from 11 to 22 kW (assuming the presence of a main fuse with a rating of 3 x 32 A, or amps, for the latter). That said, it is still very common to see 1.7kW / 1 x 8 A and 3.7kW / 1x 16A chargers installed.

It’s important to note that the electrical supply will always be measured in amps (amperage) and not in voltage. The higher the amps, the more electrical load a building can handle.

Considering that there are essentially 4 charging speeds, 22 kW falls in the lower tier

  • Slow charging (AC, 3-7 kW)
  • Medium charging (AC, 11-22 kW)
  • Fast charging (AC, 43 kW and (CCS, 50 kW)
  • Ultra fast charging (CCS, >100 kW)

What’s more, many residential buildings currently have main fuses smaller than 32 A, so it’s essential to keep this in mind when estimating at-home charging speeds and charging times.

To make a long story short, most residential charging devices rely on AC.

It’s certainly possible to upgrade a residence’s charging capabilities, but this will require the help of a skilled electrician and is not exactly cost-effective. Fortunately, it’s possible to account for amp limitations by restricting the maximum power of a charging device using the Virta admin panel. This kind of control over your EV charging points is essential to prevent dangers such as over-charging, under-charging, circuit damage, or even fire.

Different usage and capacities

EV drivers are not restricted to their private at-home charging stations and an ever growing number of public charging stations are also readily available.

Now, EV drivers will find that — although they are less convenient in that they involve a trip — public charging stations are capable of much quicker charging speeds. The reason for this is that they are meant for different usages.

When plugged at home or at the office, EVs are usually charged for many hours, and charging speed isn’t necessarily an issue. On the other hand, EV drivers expect public charging stations to charge their batteries quickly.

There are also fundamental differences between AC and DC chargers. Differences that we’ll now address.

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AC charging vs. DC charging: How they differ?

What AC chargers do

Most private EV charging set-ups use AC chargers (AC stands for "Alternative Current"). All power used to charge an EV comes out as AC, but it needs to be in DC format before it can be of any use to a vehicle. In AC EV charging, a car does the job of converting this AC power into DC. That’s why it takes longer, and also why it tends to be more economical.

All electric cars can convert AC power into DC. This is because they have a built-in onboard charger that turns this AC into DC power before transmitting it to the car battery. However, every onboard charger has a maximum capacity depending on the car, which can transfer electricity to the battery with limited power. 

Here are some other facts about AC chargers: 

    • Most outlets that you interact with on a day-to-day use AC power. 
    • AC charging is often a slower charging method compared to DC.
    • AC chargers are ideal for charging a vehicle overnight.
    • AC chargers are much smaller than DC charging stations, which makes them suitable for office, or home use.
    • AC chargers are more affordable than DC chargers.

What DC chargers do

DC EV charging (which stands for "Direct Current") does not need to be converted into AC by the vehicle. Instead, it is capable of supplying the car with DC power from the get-go. As you can imagine, because this kind of charging cuts out a step, it can charge an electric vehicle much faster.

Rapid chargers pull off their charging speeds through the use of types of DC power. Some of the fastest DC chargers can provide a fully charged vehicle in an hour or even less. The counterpart for this performance gain is that DC chargers require more space and are pricier than AC chargers.

In short, DC charging can be characterised by the following: 

  • Ideal EV charging for shortstops.
  • DC chargers are costly to install and relatively bulky, so they’re most often seen in mall parking lots, residential apartment complexes, offices, and other commercial areas.
  • We count three different types of DC fast-charging stations: the CCS connector (popular in Europe and North America), the CHAdeMo connector (popular in Europe and Japan), and the Tesla connector.
  • They require a lot of space and are a lot pricier than AC chargers.

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What EVs and PHEVs can do

Taking the above into account, it’s important to remember that charging metrics and capabilities are always rough estimates and not a given.

For one thing, charging speed will also greatly depend on the capabilities of the vehicle itself. This is because every electric car will have a different acceptance rate—if a car has an acceptance rate that is less than the supply of a charger, the car will only charge to the limit of its acceptance rate.

Choose a partner that can bring you the best of EV charging

The charging capabilities outlined above are pretty impressive, but the electric vehicle world is just getting started. Future cars will be able to charge with higher power and have bigger batteries. Charging points installed today should serve all users and be future-proof. When looking for an EV charger installer, make sure that they provide smart charging solutions that can adapt to future trends.


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