Electric Vehicles – Charging

Dr Arun Ulahannan & Prof. Stewart Birrell, from Coventry University, give an overview of electric vehicle charging in this video.

Hello and welcome to the second video of our series and this one is about cable charging for electric vehicles. Just like you take your petrol or diesel vehicle to a station to fill up, the same thing needs to be done with electric vehicles and this is a crucial part of the use of an electric vehicle and there are many ways charging can be accomplished. So we need to first learn about two things. Kilowatts and kilowatt hours.

You’ll see these two measurements a lot when talking about electric vehicles, so let’s break it down. Kilowatts is a measure of power, kilowatt hours is a measure of energy. We always measure charging speed in kilowatts. The higher the number, the faster you charge, and similarly we measure the battery size of your vehicle in kilowatt hours. And again, the higher the number, the bigger the battery of your vehicle. So let’s use these two measures to understand.

Electric vehicle charging the most common type is known as cable charging. This is where you would plug in a special cable to the vehicle and charge and there are three types of charging speeds. Slow, fast and rapid as the names would suggest, it’s all dependent on how quickly you’re able to charge your vehicle. Using that option. There is also, of course Tesla’s Supercharger network, but this is currently reserved only for Tesla vehicles, so slow charging is typically what you would find at home.

This is around 3 kilowatts. Then you have fast charges which can be between 3 and 22 kilowatts. Then you have rapid charges which are capable of speeds of 40 to 100 kilowatts. As you can see from the graph, the number of charges available in the UK has grown hugely over the last 10 years, but progress is still being made.

So practically, how long do these charges take? Well, luckily we can work this out with a little bit of maths if we know the rating of the charger we’re using in kilowatts and the size of our battery in kilowatt hours. All we need to do is take our battery capacity and divide it by the charger rating and this gives us an idea of charging time.

So if our vehicle has a 40 kWh battery a bit like the Nissan ENV 200 and we’re charging using a two kilowatt charger, then this would take us 20 hours to go from zero to a 100% charge, but if we had a rapid charger then we could charge our 40 kWh battery in just 24 minutes, which is quite a lot faster. Of course, it’s unlikely that you’ll be charging your vehicle from zero percent. You might finish the day with 20 or 30%, for example, which would then take less time to fully charge.

But this method gives you a quick way of comparing charging times using different types of charges, but there are new types of charges being developed, and one of these is wireless charging and we’ll talk more about this in the next video.

Watch Video 1

Watch Video 3