How do electric cars work?
By: Shell Energy
14 Jul 2021
While we haven’t quite reached a Jetsons-level world with flying cars, the evolution of the automobile is well and truly underway with electric cars, also known as electric vehicles (EVs). And the way they work is simple, right? Plug them in, charge them up and off you go.
An electric car has a lot going on under the bonnet. For a start, there isn’t a conventional engine to speak of, but rather an electric motor and lithium-ion battery.
When powered by 100% renewable electricity, EVs play an important role in the UK’s journey to net-zero, but not many of us could explain how they work. Questions around how to charge an electric car, hybrid options and how they compare to petrol and diesel vehicles continue to crop up.
If these questions are familiar to you, you've come to the right place. In this guide, we take a closer look at EVs and how they work.
How do electric cars work?
The name might be a giveaway, but electric cars are powered by electricity. They plug into a charge point and use electricity from the grid to fully charge.
The charge will power an electric motor inside the vehicle, and each charge is preserved in a powerful lithium battery. The electric motor inside an EV also means there isn’t clutch for changing gears, or a gearbox at all. These motors are far more responsive than most internal combustion engines (ICE), so the average EV will accelerate faster than a petrol or diesel-powered equivalent. And this also explains why EVs can feel lighter and more agile to drive.
EV use is on the rise. As of May 2021, there were 260,00 pure electric cars on the road in the UK, and last year saw an impressive 66% increase from the previous year for new electric car registrations.
Although this sounds promising, annual sales of EVs will need to increase from 110,000 currently to two million per year in the next 10 years if the UK is to reach its target of going net-zero by 2050. That’s a near 20-fold increase.
So while the numbers are moving in the right direction, there’s still more work to be done to ramp up the shift to lower-carbon transport. You can read about what we’re doing to help the UK on its path to net-zero and how we’re giving EV drivers a helping hand.
Now, let’s get to grips with what’s on the inside.
What is an electric car battery made of and how does it work?
Inside an EV is a lithium battery, which is made from carbon or graphite, a metal oxide, and lithium salt. These elements combine to create positive and negative electrodes and, when charged with electricity from the grid, they produce an electric current that powers the vehicle.
We measure electrical power in kW (kilowatts). They’re the same units of power that make our appliances work. To determine how much power a device needs to work, we use a measurement called kWh (kilowatts per hour). So whenever you boil the kettle for a cuppa, or charge your phone when the battery is low, kW are being used to make those appliances function, and we understand how much power they need by measuring those kW over time.
EVs are no different in this sense, though they’ll need a lot more kWs than your kettle to fully power the vehicle's battery.
How do you charge an electric car?
Is charging an electric car as simple as plugging into the mains? Well yes, you do plug in, and it does use electricity from the grid, but it’s not as simple as charging your phone.
Charge times depend on the type of charger you may use. The length of time it takes can also depend on the type of vehicle you have and how much charge it can take. Charging speeds for electric cars are measured in kilowatts (kW). The higher the number of watts the car can handle, the faster the car will charge.
There are few types of EV charge point speeds, ranging from ultra-rapid, rapid, fast and slow.
Slow charging is a very common method of charging EVs, used by many EV drivers and best suited to charging at home overnight. Most slow charging units are typically rated at up to 3 kW. Slow charging can be carried out via a three-pin socket using a standard 3-pin socket, or via dedicated EV charging unit. Most slow charging units are untethered, meaning a cable is needed to connect the EV with the charge point. Charging an EV via a standard 3-pin socket takes longer, so for those who need to charge regularly it is recommended that you install an EV charge point.
Fast chargers are typically rated at either 7 kW or 22 kW (dependent on a single- or three-phase grid connection). Charging times vary on unit speed and the type of EV, but - to give you an idea - a 7 kW charger can charge an EV with a 40 kWh battery in approximately 4 to 6 hours, while a 22 kW charger can do so in about 1 to 2 hours. Most fast chargers are untethered, though some home and workplace based units have cables attached, so compatibility will depend on your type of EV and charging connection type.
Rapid chargers are typically rated at 50 kW while ultra-rapid chargers can be 100kW-150kW. All rapid devices have charging cables tethered to the unit, and only compatible with EVs that have rapid charging capability. A 50kW rapid charge point can typically charge an EV from 20% to 80% in 20 minutes to an hour depending on battery capacity and the starting state of charge. With an EV capable of accepting 100 kW or more, it can take 20 to 40 minutes for a typical charge.
There are a number of charge point options available in the UK - you can opt to have one installed at home, or make use of public charge points found in various locations such as shopping centres and supermarkets, petrol station forecourts and in designated street parking areas.
Why are electric cars better for the environment?
EVs are quiet and produce no carbon emissions at the point of use, unlike petrol or diesel equivalents. That’s because EVs don’t burn any fuel.
Instead they have an electric motor that quietly works as it propels the vehicle forward. If this is powered by renewable electricity, then there are no carbon emissions from when the power was generated or used. In fact, some EVs need to have artificial car-sounding noises because they’re virtually silent on the road.
What is a hybrid car?
Electric cars aren’t the only option for buying a vehicle that runs on electricity. Hybrid cars offer a combination of electric charging and petrol or diesel. They give the option to drive using either the electric motor or a conventional engine. They emit fewer pollutants and greenhouse gases than a petrol or diesel car but typically tend to have a much smaller battery than an EV and therefore much less electric driving range.
There are just over 515,000 hybrid cars in the UK, and the number is constantly growing. If you’re buying a hybrid car, you have two options: hybrid and plug-in hybrid.
A typical hybrid car uses its petrol or diesel engines to keep the battery charged while you drive, so there’s no need to use a charge point. The internal combustion engine charges the battery once the petrol or diesel engine takes over to power the car’s forward motion.
Plug-in hybrids typically have a larger battery than general hybrids. This means, up to a certain point, they can run entirely on electrical power without the need for any petrol or diesel usage. Once the battery runs out of power, then the engine takes over, and the vehicle operates like a standard petrol or diesel car. And like an EV, a plug-in hybrid can also be charged by 120-volt household charge point.
Differences between electric and hybrid cars
The primary difference between an EV and hybrid car is fuel. While EVs run purely off electricity, hybrids use a mixture and still rely on either petrol or diesel to sometimes power the vehicle.
Why it’s worth considering an electric car
Buying a vehicle is an investment which can pay dividends over the long term. While EVs tend to have a more expensive initial outlay, they can be more economical to run than petrol and diesel cars. This is down to the fuel being cheaper (electricity is cheaper than petrol) and maintenance being more straightforward. And with tax breaks in the first year as well as certain exemptions from the congestion charge in cities such as London and other Clean Air Zones throughout the UK, EVs can often work out as the more cost efficient option.
There’s also the environment to consider. As we all become more environmentally conscious, EVs provide a cleaner option than internal combustion engines.