What is fast charging? What is rapid charging?

Fast charging and rapid charging are two phrases often associated with electric cars, but what's the difference? We explain...

If you’re just getting into electric vehicles, you may be puzzled by the different charging points and speeds available for your car. In simple terms, there are slow, fast and even rapid chargers available today, with different connectors and rates of power. Understanding the differences between these is key for any new or potential electric vehicle owner.

All three charging methods will top up your electric or PHEV with power, but the way they do so differs. More importantly for owners, so does the speed at which they recharge. As the names suggest, rapid and fast chargers work much quicker than slow chargers, meaning you’ll spend less time at the charging station and more time driving.

Read on to find out how fast and rapid chargers work, and their benefits.

How fast and rapid charging works

Electric vehicle batteries have to be charged with Direct Current (DC). If you’re using a three-pin plug at home to charge the vehicle, it will draw Alternating Current (AC) from the grid. To convert AC to DC, electric vehicles and PHEVs feature an inbuilt convertor, or rectifier.

The extent of the convertor’s capability to turn AC into DC electricity partly determines the charging speed.

All fast chargers, rated between 7kW and 22kW, draw AC current from the grid and rely on the car’s in-built converter to turn it into DC. A typical fast AC charger can fully recharge small electric vehicles in three to four hours.

To speed up the process, car companies and charging service providers have begun to build and install rapid chargers. There are two kinds of rapid charging. Rapid AC charging uses more power, at 43kW, than conventional fast AC charging, but the process is the same – AC is converted into DC by the electric vehicle’s own rectifier.

The other means of rapid charging is via DC current. In simple terms, rapid DC chargers supply DC current straight to the car, bypassing the converter, allowing the car to charge with higher rates of power. Rapid DC chargers are costlier to build, which is why their popularity is only now growing. As of August 2018, there were 3,752 rapid charging connectors (both AC and DC) in the UK.

While rapid AC chargers supply power at 43kW, rapid DC chargers work at 50kW. Tesla’s Supercharger network is also known as a DC rapid-charging unit, and works at a much higher 120kW power. In comparison to fast charging, a 50kW rapid DC charger will charge the new 40kWh Nissan Leaf from flat to 80 per cent full in 30 minutes.

Below is a rough breakdown of the basic kind of charging speeds available:

Slow AC – 3kW

Fast AC – 7kW to 22kW

Rapid AC – 43kW

Rapid DC – 50kW

Rapid DC (Tesla Supercharger) – 120kW

Can any electric vehicle use fast and rapid chargers?

The most common connectors for fast chargers are Type 2 connectors, which many electric vehicles and PHEVs are able to use. For those that don’t feature a Type 2 plug, some AC fast chargers also use a Type 1 or Commando connector.

All rapid AC chargers use a Type 2 connector, but because of the charging capacities for some electric vehicles, not all of them will be able to convert 43kW of AC power to DC. The good news is that your car will automatically limit the power to its maximum capacity, so you won’t harm your battery.

Whether your electric vehicle can use DC rapid charging depends on two factors: its maximum charging capacity and which connector types it accepts.

Rapid DC charging uses either CCS or CHAdeMO connectors (Tesla’s Superchargers use Tesla’s own Type 2 120kW DC connectors).

Electric vehicles that use CHAdeMO rapid chargers include the new Nissan Leaf, Mitsubishi Outland PHEV and Kia Soul EV. Cars such as the BMW i3, Jaguar I-Pace and Hyundai Kona EV all use the CCS standard of connectors. Look to your car’s manual or brochure to find out which connector it has.

The good news is that most rapid DC charging stations in the UK come with both CCS and CHAdeMO connectors.

Are rapid chargers more expensive to use than fast chargers?

Different charging networks charge different fees for using their rapid chargers. For example, Ecotricity, a main provider of charging stations throughout the UK’s motorway network, charges £0.30p per kWh. Polar, another provider, charges users differently with a £6 per 30min fee. Most providers charge between £0.25 and £0.35p per kWh. In comparison, the average domestic electricity price in the UK is £0.13p per kWh.

Where to find rapid chargers

Rapid-charging stations are often located in their own sites, so it’s worth getting on to websites like Zap Map (www.zap-map.com) for guidance on where to find the nearest fast or rapid-charging station.

Use the map to type in your postcode, and then use the filter at the left-hand side to identify the charging speeds and the right connector type for your vehicle. The map will also show how much each station charges, whether the charging station requires a subscription or loyalty card, and even if the station is in use.

Alternatively, both electric vehicles and PHEVs have their own database of charging stations built into the manufacturer infotainment and sat-nav.

Will frequent fast or rapid charging damage my battery?

Lithium-ion batteries, the type of battery commonly found on board electric vehicles and PHEVs, deplete over time, just like any other form of battery. And while the batteries found in laptops and mobile phones can be damaged if they are charged at high power consecutively, electric vehicle batteries won’t. This is because manufacturers have built in safe systems for the batteries to prevent damage from frequent use of rapid or fast charging. For example, the rate of charge can be automatically lowered if the car thinks too much power is being supplied to the battery too often.

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