Winter with bridge

Severe winters could hamper your electric vehicle, study finds

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Researchers based at Idaho National Laboratory have found that cooler temperatures have a significant impact on charging times for electric vehicles.

Europe is currently caught in a spate of heatwaves, which not only cause severe discomfort and a fall in productivity but also have a serious impact on public health. In Spain, temperatures are expected soon to soar well above 40°C as hot air swells north from Africa.

These dangerous heatwaves are just one example of the extreme weather forecast to become more severe in coming decades. Thanks to climate change, we may also expect dangerous storms and colder winters.

Researchers have now suggested that extreme weather could affect electric vehicles, often considered an important part of the climate mitigation effort. While electric vehicle manufacturers often provide customers with estimated charging times, these estimates do not account for extreme temperature changes.

According to the researchers, electric vehicles could take longer to charge as temperatures drop due to the impact of lower temperatures on electrochemical reactions within the cell, with integrated battery management systems limiting the rate of charging in order to prevent damage to the cell.

“Battery researchers have known about the degradation of charging efficiency under cold temperatures for a long time,” said Dr Yutaka Motoaki, an electric vehicle researcher working with Idaho’s advanced vehicles research group.

While batteries can operate under a very wide range of temperatures, for most batteries charging is affected by extreme temperature, particularly as temperatures reach and exceed the freezing point of water (0°C). Most current knowledge of how charging is affected by lower temperatures comes from lab-based experiments, rather than real electric vehicle batteries under realistic conditions. This latest study was conducted using data from a real fleet of electric taxis (Nissan Leafs) in New York.

“We wanted to ask the question: What is the temperature effect on that battery pack,” said Motoaki. “What is the effect of degradation of charging efficiency on vehicle performance?”

The researchers collected and analysed data from the taxis through approximately 500 charges across temperatures of -9.4°C to 39.4°C. They found that at cool temperatures, charging times began to increase; for instance, at 25°C an electric vehicle cell could charge to 80 per cent capacity in half an hour while at 0°C, it could charge to just 36 per cent in half an hour. As the temperature dropped further, it would take longer and longer for the battery to charge. At the very coolest conditions tested, the researchers found that charging took three times longer than it would under moderate temperatures.

This effect could have a particularly negative impact on people who make their living by driving (such as taxi drivers or delivery drivers) and so effectively lose money when they are unable to drive.

While those who are able to charge their vehicles indoors during winter – for instance, in a garage – will not be strongly affected by severe weather, those who rely on outdoor charging points are likely to find their vehicles taking considerably longer to charge.

However, consumers considering purchasing electric or hybrid vehicles should not be too put off by the fact; cold weather is also well known to impact fuel economy with petrol and diesel vehicles.

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