How Does the Cold Weather Affect EV Car Battery Performance?

At the time of writing, the UK is entering the depths of winter, with sub-zero temperatures and even snow predicted. 

For a lot of EV drivers, this will result in a noticeable reduction in the usual range of their electric car. And on top of this, many will find that their charging stopovers take longer. Charging speed seems slower than before.   

If you’ve ever wondered why this might be happening, we’re about to explore the reasons behind this apparent reduced battery performance and how best to tackle it.

Why does my car charge more slowly in the cold?

As an electric car (EV) owner, it’s likely you will have experienced trying to fast charge during the winter, and not received as quick of a charging speed as the stated power on the charger. This is in fact a very common problem. And here’s why… 

The EV runs the show

First and foremost, it is important to remember that when it comes to EVs – the car is in charge, not the driver. 

A charger can always provide its stated power, but an EV decides how much power it will accept. Essentially, electric vehicles themselves regulate the charging process to protect the battery – and so the speed of charge varies throughout a charging session. We call this an electric car’s ‘charging curve’. 

During winter, there is one core reason fast charging is slower than at any other time of the year – and that’s ‘battery temperature’. 

The temperature of an EV’s battery greatly affects the charging speed – which often drops considerably below zero degrees. An EV battery has an ideal operating temperature, preferably around 20-40 degrees depending on the car model, which can be difficult to achieve in winter. If the temperature is lower than this, it will affect both charging speed and range. This is because the electrochemical processes in the battery slow down as the temperature drops. 

Many people park their car outside or in an unheated garage, resulting in the battery temperature matching that of its surroundings. As a result, the EV must use a lot of energy to reheat the battery. 

As a rule, an EV battery won’t reach the ideal operating temperature on a normal drive-in minus degrees. So, when you come to charge your vehicle, some of the power from the charger goes to heating the battery instead of charging it. Consequently, charging takes longer when you arrive at the charging station. After charging at a fast speed for a while, the battery will have reached operating temperature, which means the range should be better and you’ll be able to fast charge at the expected speed next time.

How can you avoid slower charging speeds in winter?

It’s generally difficult to avoid cold batteries in winter, but there are some ways to avoid slow charging.

1. Preheat the battery

Many EV models offer drivers the opportunity to preheat the car’s battery, either before you go out for a drive or while you are on your way to a fast-charging station. Your car will then prioritise heating the battery so that it reaches operating temperature, meaning power won’t be diverted while charging. We highly recommend preheating your EV’s batteries if your model allows for it.

2. Wait to charge

If you’re not able to preheat your EV’s batteries in advance of a trip, we recommend waiting as long as your vehicle will allow before you carry out a charge. This way, the battery at least has time to get lukewarm – making charging both better for the battery and faster. 

It may also be a good idea to use regeneration to assist in heating up your battery. And fast acceleration can help increase the temperature – without us wanting to encourage rough driving, of course!

3. Park the car indoors

Obviously, not everyone will be fortunate enough to be able to do this, but if you have the opportunity, we’d definitely recommend parking your EV in a warmer environment. This will ensure that the batteries do not get as cold, and you do not have to spend as much energy on heating them! 

EV range in the cold weather – how can you maximise it?

As mentioned, the winter weather also leads to a reduction in the range you are used to with your EV. So how can you counteract this?

1. Preheat the car

You might not want to hear this, but the biggest energy sucker is your heater… 

In fact, Renault estimates extreme heating or cooling of your EV can reduce range by 30%. 

Therefore it might be an idea to start preheating your EV in the morning while the car is still plugged into the charger. This way the battery also gets hot when you start driving, and the car doesn’t have to use electricity to heat it up. If it is cold in the car and you haven’t turned on the preheating in the car, a seat heater is a good alternative to the heater. It requires less power and thus does not use as much of the battery as the heater does.

2. Driving conditions increase energy consumption

In the winter, the road can often be wet or covered with snow or slush – meaning that energy consumption can quickly increase by 10% or more. The surface is therefore an important reason why many people experience a shorter range in winter. Regardless of the season, it is also important to check the air pressure on your tires – too little air will increase rolling resistance and increase the energy consumption of the car.

3. Adjust your driving style

Avoid heavy braking and accelerations. Essentially, try to drive as smoothly as possible. You can save a lot of power with a quiet driving style – high speed leads to increased air and rolling resistance, which in turn increases energy consumption. If you find it difficult, you can try switching on your EV’s eco-driving program. This slightly reduces the effect when you step on the accelerator pedal, as well as automatically reducing the heat.

4. Let the EV battery get hot when you can

Remember to always charge the car when the battery is hot. The electronics in the car will protect the battery from a high voltage charge if you try to charge when it is cold – and so the car will reduce the power. Therefore, always charge the car after driving for a while and before parking it.  

Not that range can also be affected by other factors such as extreme heat, cabin load, and more. We recently looked at how long EV batteries last in detail and how you can protect their health day-to-day and long-term.