Why does cold weather affect EV batteries?

The optimal temperature for EV battery performance is between 15oC and 30oC. As the temperature drops below 15oC, the lithium ions encounter more resistance within the battery, so they move slower and don’t produce as much power as usual. That is the main reason that batteries have lower range in winter – up to 40% lower. 

There are two other contributing factors. One is that regenerative braking is not as effective when battery power is low, so your car’s ability to capture that braking energy is lower and some of that energy is wasted. That leads to lower battery performance. The second contributing factor is that cold weather means you’ll often want to turn on the heaters and the headlights. Your battery is having to work harder, with reduced capacity, so you can see why it’s important to take extra care of your EV in the cooler months. 

Here are five tips to help you care for your battery and make the most out of your EV in winter:

1. Keep your battery charged to 50% or higher

Be prepared for reduced range and lower performance by ensuring your battery is always charged to at least 50% before you leave home in winter. Even when you’re not driving your vehicle, you should maintain a base charge rate of 20% in winter. This gives you some reserve energy which may be required to start your car if the battery is very cold. 

2. Leave more time for charging 

It takes longer to charge batteries in cool temperatures because the ions are moving more slowly. Your battery can be up to 36% slower to charge at zero degrees than at 25oC. Plugging in overnight at home is an ideal way to give your battery the time it needs to fully charge. 

On longer trips, don’t assume you’ll have your usual summer range to get you between charging stations – plan to charge sooner and more often. More powerful chargers won’t always solve the problem, as onboard electronics can limit charging speed to protect the battery.  

3. Try to park your EV inside when the charge is low

Leaving your EV parked outside in cold weather can be risky. As the battery gets colder, it needs an increasing amount of power to start the car. (The same is true for petrol engines – it takes more fuel to start your car on winter mornings.) 

You don’t want to get into your car in the morning and have it fail to start, which could happen if it’s cold enough and the charge was low. Instead, park it in a warmer spot whenever you can, and don’t let it get too cold when the charge is low. 

4. Use the preheat option 

If your EV allows it, preheat your car at home before you hit the road. This not only gives you a nice cosy car to hop into, but it also means you aren’t working the battery as hard in the cool temperatures. Instead, the car heats up slowly in a warmer environment, and you won’t need to crank the heat up as high once you get going. And by warming up your EV while it’s plugged in at home rather than once you’re on the move, you’re further reducing battery drain.  

5. Switch on the heated seats and steering wheels 

Using your car’s heater in low temperatures drains a lot of power from your battery, reducing your range. Instead, switch on the heated seats and heated steering wheel if you have these options. By applying heat directly to your body, you can stay toasty warm on a cool morning without blasting hot air to warm up the entire interior. 

Stuck for charge? We can help 

If you are in Auckland, Wellington or Christchurch and your EV is too cold to start, remember you can always call AA Roadservice or contact us via the app – we now provide mobile EV charging. Out and about and looking for a charging station? Try the AA Traveller tool, which shows you the location of every public charging station in New Zealand.