How an electric car works


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How an electric car works

As emissions regulations around the globe get stronger, car-makers are focusing on the next big thing: electric vehicles. So how do they work?

Electric vehicles are garnering a lot of attention around the world, but here in Australia they haven't made much of an impact. According to the Federal Chamber of Automotive Industries, electric-car sales made up just 0.11 per cent of the total Australian new-car market in 2015, up from 0.036 per cent in 2013.

There are three main types of electric car: pure electric, hybrids and plug-in hybrids.

Clearly electric cars have a long way to go before they make a dent in local sales of conventional petrol and diesel-powered cars, but as the New York Times notesi - and countries like Norway and certain US states have demonstrated - government incentives can quickly bolster electric-car sales by providing financial subsidies to their purchase.

So how does an electric car work? There are three main types of electric car: pure electric, such as the pioneering Tesla Model S, hybrids such as the Toyota Prius and plug-in hybrids like BMW's i3.

According to Tim Williams, from the Creative Industries Faculty, School of Design Office at Queensland University of Technology, pure electric cars are the simplest of the three designs, and in the long term will become the preferred choice for electric-car buyers.

"A pure electric car is very simple," he explains. "It's a battery pack, an electric motor and the associated controller electronics. There's nothing more to them."

A vehicle like the Tesla Model S uses lithium ion batteries, the same found in many electronic devices, like laptops, arrayed in a large tray between the front and rear wheels. As Tesla outlines in its literature, although the batteries are heavy, around 550kgii, because they are mounted between the wheels, they contribute to a low centre of gravity and in theory, better handling.

Williams says a Model S has a range of around 450 kilometres between charges, and charging the battery can be done using a high speed charger in around 40 minutes.

Plug-in hybrids and conventional hybrids combine an electric motor and battery pack with a petrol or (rarely) diesel engine. The electric motor can be used at low speed in situations like start-stop traffic, and can also assist the petrol motor at higher speeds, increasing fuel efficiency.

Williams says a plug-in hybrid can be used in pure electric mode for longer than a traditional hybrid, and owners have the option of using a charger to top up the battery, something that does not exist on a conventional hybrid.

"Hybrids are good in heavy traffic, where the conditions mean the electric drive can be used to get the car up and running, and then the brakes are used to regenerate power by turning the motor into a generator as the car comes to a halt and topping up the battery."

Hybrid cars are good in stop-start traffic and so are widely adopted by taxi-drivers. Source: Flickr user jeremyg3030, https://www.flickr.com/photos/126433814@N04/, Creative Commons Attribution 2.0 Generic (https://creativecommons.org/licenses/by/2.0/legalcode), https://www.flickr.com/photos/126433814@N04/22194953019

It's because hybrids (like the Prius or the Toyota Camry Hybrid) are good in stop-start traffic that they are widely adopted by taxi drivers, who do most of their driving in those conditions. Hybrids, and even pure electric, are a less compelling proposition for freeway driving, partly due to concerns about range (otherwise known as range anxiety) and also because combustion engines tend to be quite efficient at highway speeds, says Williams.

All electric cars use regenerative braking, Williams adds, which turns braking energy and lost heat back into electricity, because it helps keep the battery charged.

"Australia has the opportunity to be a real leader in the adoption of electric cars because we are so highly urbanised," says Williams. "But as other countries have shown, sometimes it's necessary for the government to get involved to provide incentives for early adoption."



i Jolly, D., 2015, "Norway is a model for encouraging electric car sales," New York Times, October 16, 2015, viewed 15 December 2015, http://www.nytimes.com/2015/10/17/business/international/norway-is-global-model-for-encouraging-sales-of-electric-cars.html?_r=0

ii Tesla Motors, 2011, "Why is the S so heavy?" Tesla Motors Italy, Forum 8 May 2011, viewed 15 December 2015, https://my.teslamotors.com/it_IT/forum/forums/why-s-so-heavy