April 9, 2020

EVs when cold weather bites

Driving an electric vehicle in winter is like any other: the same laws of physics apply to grip when braking and cornering, and traction when accelerating. However, there are several differences that drivers should be aware of when the temperature drops.

Range

The range of an EV will reduce in cold weather. In the depths of winter, range can reduce by up to 50% from a cold start, although in typical use it’s more likely to be around 20-30%. This is particularly apparent if you’re making lots of short journeys, where the vehicle cools down between each trip.

In a petrol or diesel vehicle (ICE), waste heat from the engine is used to warm the cabin. This is one reason why ICE vehicles are only 20-25% efficient as they generate a lot of waste heat and noise. EVs, which are 75-90% efficient by comparison, do not have an engine so do not create waste heat. Heating the cabin from a cold temperature can reduce range by as much as 30% in extreme conditions.

Charging

Rapid charging can be slower in cold weather because a colder battery cannot be charged as quickly as a warm one. This means charging times may be longer on winter journeys, something to be aware of when planning an early morning start or a quick pit stop en-route. A ‘cold-soaked’ battery may not charge at all until it is warmed up by the charger, but there are ways to avoid this (see smart charging tips).

Battery

Batteries need to be kept warm to perform optimally, which means they either need to be warmed up using their own energy or, ideally, pre-warmed via a chargepoint.

Batteries also need to be kept warm while driving – even if you’ve been driving for an hour with the heater on, the inside of your windscreen will still be cold to touch, and so will the battery underneath the vehicle. Therefore some energy will be used purely to keep the battery at operating temperature.

Braking

Regenerative braking can reduce in cold weather, because this is also linked to battery temperature and charging. This means the vehicle may feel different to drive in cold weather, requiring more manual braking from the driver as the effectiveness of regenerative braking is often reduced.

Smart charging tips
If you know what time you’re leaving in the morning, make sure your overnight charge finishes as close to this time as possible. This will mean the battery will be warmer because of the charging activity, so you won’t lose (as much) range by the vehicle having to warm the battery from its own energy reserves. You should also feel more regenerative braking as a result, which is good for range.

Pre-conditioning: This is where you pre-heat the vehicle before setting off, but from the mains electricity supply (while charging) rather than by using the battery. Another benefit is you’ll never have to scrape your windscreen again – pre-heating the vehicle’s cabin also defrosts all the windows, which is a welcome bonus.

Contributed by Volkswagen Financial Services’ fleet division.