How does cold weather affect electric vehicles?
The 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 (called ‘ions’) between them. Charging moves the lithium-ions from the cathode to the anode and discharging (while driving) moves them back the other way.
Vivienne Kerry, Business Manager, EV Connectors further explores.
Like all chemical reactions, that process varies depending on the temperature of the components. Most studies suggest lithium-ion batteries perform best between 10 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 falls below 10°C, the flow of ions slows down and this changes the speed at which it can take on energy and supply it to the motor.
How does winter affect electric vehicle performance?
As a driver, you’ll probably notice two symptoms from a cold battery:
• Reduced range: Lithium-ion batteries drain more quickly when they are cold. A group test carried out by What Car found electric vehicles lose between 15 and 20% of their range during typical wintery conditions (between 3 and 6°C) and 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 than at 25°C, which means the half-hour stop you’re used to making in summer could take 40 minutes or more in winter.
What are electric vehicle manufacturers doing about this?
Massive investments in battery research have delivered longer ranges at lower cost over the last decade, and manufacturers have introduced features that help mitigate some of the effects of winter weather on their latest models.
Whereas air-cooling was the norm ten years ago, most new electric vehicle batteries use a liquid coolant to keep the cells within their optimal temperature range. It enables much faster charging speeds without overheating, but also means the vehicle can bring the battery pack up to temperature before you set off.
Cabin heaters have also become much more efficient, as these were energy-hungry systems which exacerbated the seasonal drop in range. Lots of new models are available with a heat pump, which scavenges warm air from the powertrain and outside the vehicle, then compresses or expands it regulate the cabin temperature more efficiently. Hyundai says just fitting a heat pump to the Ioniq EV extended the car’s range by 19%.
How can EV drivers maximise their winter range?
A slight drop in performance is unavoidable in freezing conditions, but there are some steps drivers can take to mitigate the effects on their electric vehicle:
• Use your 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 your vehicle doesn’t have a heat pump
• Preconditioning: Most EVs can be programmed to warm the cabin, bring the battery up to temperature and even de-ice the windows for a pre-set departure time. If it’s plugged in, then it’ll use mains electricity instead of the battery and you’ll still set off with your full range intact. Parking indoors or using a cover also both lighten the load on your heaters at the start of your drive
• Plan your charge stops: Warmer batteries take less time to charge, so try to avoid rapid charging shortly after a cold start. Some MG and Tesla models can heat the cells to the right temperature while you’re enroute to the chargepoint
• Check your tyres: Underinflated tyres are a safety risk and impact the range of an EV, so they should be checked at least every fortnight throughout the year. However, Continental claims tyres lose a couple of PSI for every 10°C drop in temperature, so it’s doubly important to keep an eye on them during a cold snap