Feature: Electric vehicles
How
does cold weather affect electric vehicles?
By Vivienne Kerry, Business Manager – EV Connectors, Foremost Electronics
W
inter can have a big effect on an electric vehicle’s performance; so, what does cold weather
do to its battery? Te lithium-ion cells found in most
electric vehicle battery packs use a chemical reaction to store and release energy. Each has positive (cathode) and negative (anode) terminals, with a separator and liquid electrolyte to control the flow of electrically- charged particles (ions) between them. Charging moves the lithium ions from cathode to anode, and discharging (while driving) moves them back the other way. Like all chemical reactions, the process
varies, depending on the temperature of the components. Most studies suggest lithium-ion batteries perform best between 10°C and 30°C, and peak somewhere in the middle of that range – in fact, new vehicles are tested for range and efficiency at 23°C. If the battery temperature falls below 10°C, the flow of ions slows down, changing the speed at which the battery can take on energy and supply it to the motor.
18 March 2023
www.electronicsworld.co.uk
Winter performance As a driver, you’ll probably notice two symptoms of cold battery: • Reduced range: Lithium-ion batteries drain more quickly when they are cold. It was found that electric vehicles lose 15- 20% of their range during typical wintery conditions (between 3°C and 6°C); that drop in efficiency will also be reflected in higher per-mile charging costs.
• Slower charging: By slowing the chemical reaction within the cells, freezing conditions also result in slower charging times, which is most noticeable during mid-journey top-ups. A 2018 study by the Idaho National Laboratory found electric vehicles took 36% longer to charge at 0°C than at 25°C, which means the half-hour stop in summer could take 40 minutes or more in winter. Te question is: What can electric vehicle manufacturers do about it? Over the last decade, enormous
investments in battery research have delivered longer ranges at lower cost, and manufacturers have introduced features that help mitigate some of the effects of winter weather on their cars. For example,
air cooling was the norm ten years ago, but now most EV batteries use liquid coolant to keep their cells within the optimal temperature range. Tis allows much faster charging without overheating. Cabin heaters have also become much
more efficient, as these were energy-hungry systems that aggravated the seasonal drop in range. Many new models are available with a heat pump, which scavenges warm air from the powertrain and outside the vehicle, then compresses or expands it to regulate the cabin temperature more efficiently. Hyundai claims that just fitting a heat pump to its Ioniq EV extended the car’s range by 19%.
Maximising winter range A slight drop in performance is unavoidable in freezing conditions, but there are some steps drivers can take to alleviate the effects on their EV, such as: • Use the heaters sparingly: Heated seats and steering wheels are a faster and more efficient way to stay cosy than trying to warm the entire cabin using the fans – particularly if the vehicle doesn’t have a heat pump.
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