How do self-charging cars work?

Toyota, Lexus and Kia use self-charging as a term to describe their mild hybrids.

Mild hybrid doesn’t sound as exciting or technologically advanced as a self-charging car, which is probably why their marketing departments opted for the more mysterious and intelligent-sounding self-charging terminology.

How Do Self-Charging Cars Work?

A self-charging hybrid has a small battery and an electric motor. When the vehicle brakes, the initial phase of braking is used to charge the battery. Brakes (disks and pads) then kick-in after.

This is a basic form of regenerative braking (or regen) something plug-in hybrids (PHEVs) and electric vehicles (BEVs) do too, but to a greater degree and effectiveness.

The small amount of energy recovered from braking is then able to be used to drive a limited distance.

What Powers a Self-Charging Hybrid?

Exhaust pipe emissions on a self-charging car

Unfortunately, a self-powered car breaks the laws of physics, as the energy must come from somewhere. In one of Kia/Lexus/Toyota’s mild hybrids, the power comes from burning fossil fuels – the petrol in the internal combustion engine.

This means self-charging cars are 100% powered by petrol. All the propulsion achieved is down to petrol – since the cars don’t plug-in.

If we refer to mild hybrids as self-charging, we should really refer to all petrol and diesel cars as self-charging, since these cars don’t need plugging in to charge their 12-volt battery which powers the wipers, headlights and other electrical ancillery services.

How Far Can A Self-Charging Car Travel?

Toyota et al claim that their mild hybrids can be driven over 50% of the time on “pure electricity”. That makes them seem awfully green, given we tend to associate electricity with being green and petrol with being polluting. This claim is misleading for two reasons:

  1. It’s crucial to remember that Totota reference time not distance – if you drive in stop-start traffic, the engine might be off for a large proportion of the time as you’re stationary. Some of the slower speed driving may be achievable using the battery, but because the battery is very small, it will drain extremly quickly and require recharging – so the petrol engine turns on. In terms of distance driven, I’d estimate only around 5-10% of miles/kilometers are driven using the battery.
  2. All the electricity used to driver is generated by burning petrol, so it’s certainly not the clean energy you can get from the grid or solar on the roof of your house for example.

Do Self-Charging Cars Exist?

Will we ever see a car that can power itself? In the Toyota sense of self-charging, no. It’s not possible to drive a mild hybrid without putting petrol in it.

Lightyear One

However, there are projects like Lightyear One, working to create cars that you may never need to plug-in! These are pure electric cars (not hybrids, so no fossil fuels) and can be charged by plugging-in, or from the solar panels built into the roof, bonnet and boot! ☀️⚡🔋🚗

Lightyear are aiming to be able to charge an impressive 12 kilometres (7 miles) from 1 hour of sunshine charging – using the solar panels on the roof! For those who drive short distances, or only travel infrequently, that could mean you’d never need to plug-in!

More info on the Lightyear One in this Fully Charged video.

Should Self-Charging Be Banned?

In Norway (home of the EV, where over half of cars sold in 2020 were fully electric) they’ve banned adverts that reference “self-charging” believing the term is misleading.

I believe marketing a petrol car (100% powered by fossil fuels) as self-charging should be banned, as it’s extremely misleading. It makes polluting cars that burn fossil fuels seem cleaner and if you don’t do your research, you might think you’re doing your bit to look after the environment when actually, nothing could be further from the truth.

How many miles per gallon do electric cars get?

Electric cars aren’t powered by diesel or petrol, so they don’t have an official miles per gallon figure. That said, there are ways of working out how efficient they are and even give them a rough miles per gallon.

How Many Kilowatt Hours is in a Gallon of Petrol? ⛽

The US governments fueleconomy.gov website calculates 1 (US) gallon of gasoline is equivalent to 33.7 kilowatt hours of energy – or kWh.

A US gallon is 3.785 litres, whereas in Canada and the UK a gallon is 4.546 litres. This means a (UK/Canadian) gallon of petrol is equivalent to 40.5 kWh of electricity.

Each litre of petrol is equivalent to 8.9 kWh.

Toyota Prius vs Nissan Leaf MPG

The Toyota Prius was once regarded as the sustainable choice for environmentally conscious drivers, but in recent times its crown has slipped a little. This might be partly because of Toyota’s inaccurate branding, claiming that it sells “self-charging cars”, when in reality a (very small) battery is charged by recovering motion which was achieved by burning petrol or diesel. That’s how most cars charge their 12-volt battery, it’s not self-charging! 😂 It’s also because electric cars are now more viable and mainstream.

The Nissan Leaf is currently the top-selling electric vehicle of all time (at least until the Model 3’s first quarter sales are released) so let’s use that for the comparison. An “efficient” hybrid vs an electric vehicle, how do they compare?

The Nissan Leaf

The Totoya Prius achieves 62.4mpg (UK/Canada) using 4.5 litres to travel 100 miles. The Nissan Leaf by comparison achieves the equivalent of 129.7mpg (UK/Canada) taking just 2.2 litres to travel 100 miles.

This highlights the efficiency of electric vehicles.

The Leaf uses less than half the energy of the Prius (the previous “gold standard”) to travel the same distance.

Efficiency

Internal combustion engine (ICE) powered cars convert around 12-30% of the petrol or diesel they consume into forward motion powering the wheels. This is because an ICE car loses over two-thirds of its energy through heat 🔥 and the transmission of power through the drivetrain.

Even the most inefficient electric vehicles translate at least 60% of the electricity stored in the battery into forward motion. If driven using regenerative braking (to re-capture energy, rather than scrubbing it off via breaking) EVs can be around 90% efficient!

How Big is an Electric Car’s Fuel Tank?

Electric car battery and powertrain

Here’s another interesting question, if an electric car had a fuel tank, how big would it be?

The Tesla Model 3 Standard Range Plus has a 50kWh battery, so if one US gallon of gasoline/petrol is equivalent to 33.7kWh, then the Tesla Model 3s equivalent petrol fuel tank would be 1.48 US gallons – or 5.62 litres.

That’s right, an electric car can achieve a range of 200 miles (275 if driven carefully in warm weather) on less than the equivalent of 6 litres of petrol!

You can also compare cars on a cost per mile basis, which is what I’m going to write about next, with the help of the new electric Mini!

Win a Solar Go Go Car to celebrate The Future Car Challenge

Petrol cars have no future. That is a fact, in 50 years time there will be no crude oil left on planet earth (assuming current consumption rates don’t decrease) therefore there will be no oil left to make petroleum or diesel.

Biofuel, hydrogen, LPG and electric cars are the future, there is no doubt about that. Right now there are many hybrid cars which use petrol with another power source, but in the future, petrol from natural oil will be no more.

There are of course other ways you can power cars, using compressed air is one method as is water-cell technology. These are not however currently concepts in mass production. If you follow those two links, you will find posts written by Jonny on the concepts mentioned.

Arguably the greenest option for the future is electric cars. The electricity used to power the cars can be generate from renewable sources, (it isn’t necessarily, but that is an option) and electricity from renewables is a lot less damaging to the planet than energy generated from the extraction and burning of fossil fuels – be it in on the micro scale inside an engine of a car, or on a macro scale in a network of power stations.

Electric cars are starting to look more and more normal, (in the past some have looked somewhat abstract!) and are becoming more efficient every year.

The Future Car Challenge

This year, British Gas (the company who installed Remote Heating Control in my home) became an official partner of The Future Car Challenge. The Future Car Challenge is an annual event, which showcases the latest developments in the electric car industry. This year, members from the British Gas team drove fro Brighton up to London, with the aim of using the least amount of energy as possible, using the latest electric cars. The team included comedian Robert Llewellyn, Ben Collins, (A.K.A. ‘The Stig’), and Commonwealth gold medal swimmer Ross Davenport.

The Future Car Challenge Ross Davenport

Ross Davenport playing his part in the British Gas Future Car Challenge

British Gas are setting up a national charging network, to help increase the viability of electric cars. A charging network is as vital to electric cars as service stations are to petrol and diesel cars. Some electric cars do have the ability to transfer energy generate from breaking into electricity, (as seem in Formula 1 cars) however this alone isn’t enough to power them, so electric recharge points are essential.

Here is a statement from British Gas on their involvement with electric cars:

The Future Car Challenge Robert Llewellyn

Robert Llewellyn taking part in the Brighton to London Future Car Challenge

“British Gas is dedicated to making the world a more sustainable place now and in the future. We are leading the way in providing expertise and charging solutions in the Electric Vehicle market through partnering with Nissan, Renault, Hitachi Capital, Toyota and Vauxhall.

British Gas’ dedicated charging solutions are safer, convenient and more compatible than plugging electric vehicles directly into the mains supply socket at home. Not only do we offer charging solutions that can cut charging times by around a third, but British Gas also offers its customers specially designed tariffs to help them charge for less.”

For more information on The Future Car Challenge, check out this article on British Gas’s blog. The article also has an embedded video of the event.

The Giveaway

To celebrate the event, we have five solar power car sets to giveaway, courtesy of British Gas!

The prize is a John Lewis Solar Go Go Car, (click the link for more info) a cool kit from which you can build your own solar powered car! Okay it isn’t quite as good as an electric car, but it looks great fun, and could make a fantastic Christmas present…

John Lewis Solar Powered Car KitThe giveaway will run for 8 days, from today until the end of next Wednesday (12.00am on Thursday the 13th).

The prizes will be sent out by British Gas to the UK only, so if you don’t live in the UK I am afraid you can’t enter. If you have an address in the UK you can get the prize sent to if you win, you are in!

How To Enter

It is really easy to enter the competition, all you need to do is enter an email address we can contact you on (if you win) in the Rafflecopter widget below. If you like the blog on Facebook, follow us on Twitter or are subscribed to our feed via email, then you can gain some extra entries.

Want a Solar Go Go Car kit? Enter below!

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Winners will be emailed on Thursday the 13th to let them know that they have won, and will be announced on the blog shortly after.

Good luck everyone!