Extremely high temperatures or cold temperatures cause EVs to lose range and battery life by affecting the speed of chemical processes in the battery.
Electric vehicles (EVs) are powered by some of the most sophisticated battery systems available today. Improvements in battery technology have made it possible for newer EVs to be on par with internal combustion engine vehicles in terms of performance and range.
But just like other battery systems, the battery units inside EVs enjoy operating in a fixed range of temperature for maximum efficiency.
Most EVs use a lithium-ion graphite anode battery. These are the same kind of batteries that you find in modern electrical appliances like your smartphones, laptops and more but just scaled up to drive powerful motors.
If you've regularly used your electronic devices in either extremely hot or extremely cold temperatures, you would have noticed that their battery life changes quite a lot. In addition to that, fast charging often seems less effective and charging in general is slower.
This is also true for EVs. Extremes in temperature can not only reduce the range of your vehicle but also shorten the battery life.
The reason behind this is simple. Lithium-ion batteries generate power through chemical processes. Heat changes the rate at which these chemical processes occur, often disturbing the careful equilibrium set inside the battery units. Battery units in most EVs have battery management systems that try to keep the temperature stable for this reason.
When operating in temperatures below freezing, EVs can lose 10-12 percent of their range, according to data from the American Automobile Association (AAA), a non-profit federation of motor clubs in North America. If climate control is used within the car, the range can drop by a massive 40 percent.
In similar temperatures, charging time can be increased by as much as 400 percent depending on the make and model of an EV.
While these changes are temporary, charging EV batteries (or any lithium-ion batteries) when they are below freezing can trigger long-term damage to the battery through lithium build-up at the anode due to the movement of lithium-ions slowing down. Most modern BMS heat up battery units to above freezing before starting the charging process.
At the other end of the temperature spectrum, lithium-ion batteries also struggle at very high temperatures. This is because the 'unwanted' reactions within a battery are now occurring faster, draining range and longevity from a battery system.
Charging at higher temperatures should be avoided as they cause significant battery degradation through damage to the anode due to increased diffusivity, and also speed up the formation of the Solid Electrolyte Interphase (SEI).
These threshold temperatures on either end of the spectrum are dependent on many factors – battery chemical composition, the BMS, battery physical attributes, etc. It's for this reason that EV owners should carefully read their owner's manual to learn about the safe operating and charging temperatures for their vehicles.
However it's not all bad news because if your EV is operating at the optimum temperature (20°-21°C), it will often be 'overperforming'.
“At optimal temperatures, EVs are performing better than their rated range, peaking at 115 per cent at 21.5C. So, most EV owners are exceeding the rated range of the vehicle in peak temperature conditions. As you turn up or down the temperature, however, the loss of range is apparent,” said Charlotte Argue, from vehicle monitoring and telematics service GeoTab, to the Irish Times.