The time it takes to charge an electric car remains one of the hottest debates around EV ownership. And we’re here to clear the air.
Slow, Fast And Rapid Charging – What Does It All Mean?
As the EV charging infrastructure has developed – influenced both by growing demand and accessibility to more powerful electricity sources – the industry has been able to offer electric car owners 3 different rates of electric car charging: slow, fast and rapid.
Whatever kind of charger you’re plugged into, your EV will always be able to top itself up. The rate of that top up is, as you might have guessed, influenced by the rating of the charger you’re using. Slow means slower and rapid means… You get the idea.
So Why Are There Different Speeds? (The Sciencey Bit)!
It’s a good question with a simple answer: to charge a car more rapidly you need more power in the form of what is known as DC or Direct Current.
But slow chargers – the type you can have installed at your home – don’t have access to Direct Current because your home cannot supply it. It runs on what all British domestic users have access to: 240 Volts of Alternating Current or ‘AC’.
So your home charger will take the AC from your home supply, pass it through the cable to your car where a built-in convertor changes the supply to the DC current that the batteries actually need to charge.
And because AC packs less punch to start with than DC, when the in-car convertor swaps it over from one to the other, the DC charge now going into your batteries also packs less punch. Which means more gentle – and slower – charging times.
Home Charging Is Kind On Your Car - And Cheaper Too...
A 7kw home charger is kinder on your car’s battery pack because it creates less heat during the charging process, which means longer life.
It’s also cheaper to charge your electric car at home. Sometimes a lot cheaper! Unless you have access to free charging (perhaps at work or at a supermarket?) then by far the most cost-effective way of charging your car will be with a home charger.
Home charging is rated at either 3 or 7kW. The cheapest home chargers offer 3kW rates which is the sort of speed you might expect if you used a 3-pin plug from your house (but didn’t have anything else in the house running at the same time).
If you want to double your home charging speeds then go for a 7kW charger. It will cost you more to install – but the same rate to run as a 3kW unit.
If you think you will be putting in more miles and your electricity requirements will regularly be high then 7kW gives you the assurance that a nightly charge will almost definitely get you back up to speed.
With special deals now available for EV owners from many electricity suppliers, the cost of charging your EV from home can be as low as 2p per mile – that’s a tenth of the rate to run more traditional petrol or diesel equivalents.
And then there’s the simple fact that a nightly top-up at home means your car is likely to only ever need shorter charging times – even from a slow charger.
There is, though, no escaping the fact that slow does mean slow and there are going to be times when you’ll want to give your electric car a boost in charge that you can measure in minutes not hours...
That’s where the fast and rapid charging networks come in.
2 Main Factors Influence The Charge Time Of Your Car:
The battery size - This is shown as a kilowatt Hour figure (or kWh)
The charger power rating - This is shown in kilowatts (kW) and can vary from a slow 3kW charger to a very rapid 150kW charger.
To calculate your electric car charge time, you need to divide the battery size by the charger rating. For example: A 70kWh battery on a 7kW home charger will go from empty to full in 10 hours.
How Fast Is A Fast Charger?
Fast chargers – you’ll see them labelled between 7kW, 22kW and sometimes 43kW – also use AC current from the electricity grid, so you are still dependent on your car’s convertor to flip that AC into DC.
And the ability of your car’s convertor to do that job has an effect on the charging speed. Some convertors can’t turn all that AC power into equivalent DC, so will be limited to charging at a reduced rate.
In other words a 22kW or 43kW AC charger might, in reality, feed your battery at 10-12kW if that is all the convertor can handle. If you think you might be using fast AC chargers regularly then it’s worth enquiring to see if the car of your choice can convert higher AC currents.
Regardless of what you’re driving, fast AC chargers are still one of the most common solutions found on the public network and will give your EV a real boost compared to home charging. A 22kW fast AC charger can fully recharge an EV with a smaller battery pack in 3 to 4 hours.
How Fast Is A Rapid Charger?
If you come across a rapid charger on your journey then there are 2 important distinctions for you to understand.
First all rapid chargers are rated from a minimum of 50kW (and are now promising speeds as high as 350kW) and all provide DC current direct to your car’s batteries.
By converting the current into DC before it leaves the charger, they can bypass the car’s AC/DC convertor and hence offer the fastest possible charging times.
DC rapid chargers are more expensive to use but there are now over 2,500 rapid-charging locations in the UK and that number is set to grow, er, rapidly.
Again, it’s important to check whether the vehicle you’re interested in can use DC rapid charging. Whether it can or not comes down to two factors: its maximum charging capacity and the DC connector type that it is able to accept.
To use DC charging your car will need to be able to connect via either a CCS or CHAdeMO plug. That’s not as challenging a prospect as it sounds, as nearly all rapid chargers in the UK can be used via either system so the likelihood of you being unable to connect is remote.
And how fast are they? Well - take the commonly quoted 20-80% charge cycle and a 50kW Rapid charger will give the 52kWh battery in a Renault Zoe a 60% boost in just over half an hour.
But an 80kWh battery in a Porsche Taycan can in theory get a full charge in less than half an hour if you use a 150kW rapid station. Remember, though, that in reality charging from 80-100% of your capacity on a rapid DC charger will take longer - it’s not a straight line to get you from 0-100%.
Did You Know?
CHAdeMO connectors are most commonly used by Japanese carmakers to hook up to rapid chargers. The name comes from the Japanese phrase: O cha demo ikaga desuka, which loosely translated means ‘Fancy a cup of tea?’
It’s a nod to the amount of time you’ve got while you pop your car on the rapid charger at the motorway service station…
Want to know more? Take a look at our in-depth guide on everything you need to know about charging electric cars.