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Range anxiety is psychology
Two cars, same distance
After a long drive down to Wales and back in a Lotus Eletre, which has a 112 kWh battery and a range of about 300 miles, the driver watched the charge fall to 16% as the warning lights turned amber. The range left was about 58 miles.
His wife's Mini Cooper Electric has a battery of about 28 to 30 kWh and a range of about 100 miles. She drives around at 56% charge, which is a range of 56 miles, all the time without the slightest anxiety.
Psychology versus physics
The same distance felt alarming as a percentage and ordinary as miles, so range anxiety is much more a matter of psychology than of physics. The laws of physics are set in stone to a large degree, and the laws of psychology are magnificently malleable.
Billions of dollars a year go into batteries with higher energy density, which is a good thing. If the only way to ease range anxiety is more range, though, electric cars end up heavier and more expensive than they need to be, with 50 kilowatt hours sitting outside the house 95% of the time doing nothing. Reducing the anxiety could be cheaper.
Why does a percentage feel scarier than miles?
A dashboard percentage invites a comparison with a full battery, so 16% reads as nearly empty even when the miles left are plenty. Phones have also taught people to treat low percentages as warnings, and many devices turn the indicator red at around 20%. In 1981, Daniel Kahneman and Amos Tversky showed that identical outcomes described in different words, such as lives saved versus lives lost, reversed what people chose.
Why do bigger batteries make cars heavier?
Lithium-ion packs in cars store roughly 150 to 250 watt-hours per kilogram at pack level, so a 100 kWh pack weighs somewhere around 400 to 650 kilograms. A heavier car needs more energy to move each mile, which eats into the range the extra cells were meant to add. Heavier cars also need stronger structures and wear their tires faster.
Why does speed cut an electric car's range?
The aerodynamic drag on a car grows with the square of its speed, and the power needed to overcome it grows with the cube. Doubling speed multiplies the drag force by four. In stop-and-start traffic, regenerative braking returns some energy to the battery, which steady motorway driving rarely does.
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