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How does EV charging work?

Oliver Johnson, from ABB, the world’s leading supplier of electric vehicle (EV) charging points and title sponsor of the FIA Formula E Championship, answers our questions on EV charging.

To understand how EV charging works, you need to know that there are two types of electrical power: AC (alternating current) and DC (direct current).

The electrical power grid runs on AC, whereas batteries use DC. That means you need a power converter to take AC from the mains and turn it into DC to charge batteries.

First-generation EVs were designed to plug into a domestic socket, with an AC-DC converter inside the car body. However, batteries in the latest EVs are bigger for longer range and drivers want faster charging.

This relies on having more powerful converters, which are too big to fit under the bonnet. That’s why we have AC chargers for use at home and other sites where cars park for several hours or overnight. We can also find more powerful DC chargers by the roadside for faster charging. These DC chargers contain the same technology as the ones used in the ABB FIA Formula E Championship.

There are also different standards for DC chargers. CCS and CHAdeMO are the most common. The difference between them is the shape and configuration of the plug and the ‘electronic handshake’ that needs to take place between the car and the charger before charging starts. However, they deliver the same DC power.

What is the right type of charger for home or long-stay parking at work?

Many homeowners and businesses have a private off-road parking space or garage.

If they plug into a domestic 230 Volt supply via a 13 Amp socket, they can draw up to 3 kW. That’s fine for many drivers as the average car travels only 12 miles per day and only needs topping up.

But if you drive further, you’ll need more power for faster charging. That’s why we provide more powerful AC chargers. These typically deliver 6-7 kW, although some reach 22 kW. Some of these chargers qualify for a government grant of up to £350 if they’ve been approved by the Office for Zero Emission Vehicles (OZEV).

How can I choose the right fast or ultra-fast public charger?

The UK’s network of fast and ultra-fast chargers is based on DC charging. DC chargers deliver anything from 20 to 350 kW.

At the lower end of this scale, 20-25 kW DC chargers are designed for drivers who are planning to park for 1-3 hours. That makes them ideal for offices, commercial buildings, car dealerships, blocks of flats, hotels and hospitality sites.

For the next step up, 50 kW DC fast chargers are a good match for sites where cars are parked for 20-90 minutes. Examples include high turnover parking sites, supermarkets, big box retailers, restaurants and convenience sites.

And at the top end, chargers rated at 150-350 kW are designed for motorway service stations and suburban sites where drivers will be able to add 200 miles of range in 20 minutes.

For example, the City of York Council has invested in ultra-fast 175 kW DC chargers at two new HyperHub sites. The aim is provide fast no-fuss charging for people living in the city’s terraced housing who don’t have off-road parking for their own AC charging point.

And in Essex, GRIDSERVE recently built a new Electric Forecourt dedicated to EV drivers with 12 chargers able to deliver up to 350 kW with DC charging, as well as 22 kW AC units.

As a driver, the rule of thumb is that you should go for the charger that is the best match for how long you’re planning to stay.

Green Car Guide’s ABB Terra AC wallbox

ABB manufactures some pretty heavy duty rapid chargers, but it also provides home chargers, and Green Car Guide uses one to charge a different EV on test every week. It’s ABB’s new AC charger, ‘Terra AC’. This was fitted by a qualified charger installer, who reported no problems with the installation, and the installation was inspected for a quality check, and again, all was OK.

Home chargers can come with a charging cable attached – which is called ‘tethered’. The ABB Terra charger doesn’t come with a cable attached, so you use the cable that’s supplied with the EV. And some chargers automatically start charging when you plug the cable in, however with the ABB Terra you initiate the charging with an app on your phone called ChargerSync. This connects to the charger via Bluetooth and you press a button to start charging. The app also allows you to do a lot more, such as to schedule charging, and it provides a range of data such as energy consumption.

Critically, the ABB Terra AC has smart functionality, which means that its power usage can be managed if required.

The ABB Terra charger has worked perfectly well with a different EV every week, and it looks quite unobtrusive compared to some chargers.

ABB ChargerSync app

ABB ChargerSync app