Why are electric cars less efficient in winter?

The lighter impact of electric cars on the environment is a significant motivation for the greater use of battery-powered vehicles.

But did you know that it’s a two-way relationship, as the environment itself has an impact on the effectiveness and efficiency of electric vehicles.

In much the same way that petrol cars perform better in certain atmospheric conditions, EVs operate at their most efficient within an optimum temperature window, offering longer driving range and faster charging times in moderate climate conditions compared to extreme cold and hot weather.

Why? Well, let us explain, and, at the same time, provide some handy hints on how to maximise the performance of an EV depending on your location and at different times of the year.

It doesn’t matter what type of engine you have under the bonnet, the production – or storage – and delivery of power is greatly affected by the environment.

In a conventional combustion engine, the engine directly inhales oxygen from outside of the vehicle to mix with the petrol and create an explosion that pushes the piston down to create energy.

Put simply, the more oxygen it can get the more efficient the explosion will be. Therefore, as cooler air can carry more oxygen than warmer air and the atmosphere is more dense at sea level than it is at higher altitude, a car will naturally produce more power and have better fuel economy on a crisp autumn morning near the coast than it will on a summer’s day in the mountains.

While electric cars have much simpler powertrains, and do not require the direct input of oxygen to produce power, their ability to receive and deliver electrons to and from a lithium-ion battery – and store energy – still involves a chemical process that varies in its efficiency across a range of temperatures.

A battery requires both a cathode and anode that are bathed in an electrolytic fluid to transfer energy.

And, just like the oil in an engine, the electrolytic fluid is more sluggish in colder temperatures, slowing the battery’s ability to receive a charge (which increases the time it takes to recharge the battery) and discharge (which reduces performance to the electric motor and reduces driving range).

At the other end of the spectrum, extreme heat will have an equally adverse effect on the performance of a battery electric car.

Naturally, where you live – or where you’re driving – will dictate the efficiency of an electric vehicle.

Battery-electric vehicles operate at their best in moderate climates between 10-34 degrees Celsius, which – we are a lucky country – covers most of Australia’s major metropolitan areas for most of the year.

For those who may experience the opposite extremes of local climatic conditions, according to research conducted by Stanford University battery efficiency only drops below 80 per cent at less than 0 degrees Celsius and above 40 degrees C.

What that means is, for example, if you’re driving a Nissan LEAF with a 40kWh battery and a rated driving range of 270km from Canberra to the Snowy Mountains for a weekend of skiing in the middle of winter you may actually only have 240km of range.

And when it comes time to recharge, it is likely to take 5-10 minutes longer than the quoted 60 minutes it takes to top-up the battery to 80 per cent.

While we’re not expecting a high take-up rate of EVs in Lightning Ridge or Coober Pedy any time soon, the extreme heat of the Australian outback will also reduce range and increase charging times.

Logically, having the heating and/or air-conditioning running to compensate for the outside temperatures will also sap power from the battery and reduce driving range.

The latest generation of electric vehicles have advanced thermal management systems to ensure the battery remains within its optimum operating temperature – on the road and even before you drive away.

In some cases, it will use a portion of energy to turn the heater on and warm up the battery before you start the car. From then on, it will divert air from the climate control system when the battery needs to be cooled.

Higher-tech thermal management systems involve liquid cooling the battery pack to maintain consistent temperatures, much like a radiator system does in a combustion engine.

While cooling the battery is critical, it happens automatically. However, it is important to note how beneficial it is to pre-condition the battery before driving or recharging as this will not only ensure better immediate performance on the road and shorter charging times but it will also improve the long-term health of the battery by reducing its rate of degradation.

Some EVs allow the driver to remotely start the vehicle (with the doors remaining locked) via an app or the key fob to do this. If not, warm the battery pack before any spirited driving immediately after leaving the driveway and try and prevent rapid-charging the vehicle in cold weather before the battery is warm.

Extreme temperatures will also have an effect on the regenerative braking performance of an electric car.

That’s not to say that the electric motor’s braking ability is degraded in cooler temperatures. It means that the battery will accept less of the energy recovered.

So, there you go, an understanding of how today’s environment has an impact on electric cars and how to maximise the efficiency of an EV depending on where you live and where you drive.