Range indicators: kilometres or battery percentage?
Electric vehicles (EVs) have two indicators that show you how much energy is left in your battery: kilometres or percentage charged. Unfortunately, these numbers aren’t as accurate as the gas gauge in a vehicle with an internal combustion engine (ICE). In this blog post, we’ll explain range indicators in more detail and explain when it’s best to use which number.
How is a battery’s range calculated?
When purchasing an EV, you’ll likely review this guide from Natural Resources Canada (NRC), which gives you ranges for EVs listed in kilometres. What’s important to note is that these values are the laboratory testing results, so the tables display only estimates.
Just like an ICE vehicle uses more gas during city driving than highway driving, your EV will use different amounts of electricity depending on where, when, and how you drive.
However, unlike an ICE vehicle, EVs have regenerative braking, which transfers kinetic heat into electricity. This added function fuels the battery, adding to your range, though it’ll have a stronger effect during city driving than on the highway.
How are EVs tested in a laboratory?
Fuel consumption ratings are developed from standardized testing in a laboratory because testing every vehicle in real-world conditions creates too many problems.
For starters, testing every vehicle manufactured in or imported into Canada would be too expensive. Second, setting up testing to account for differences in driver behaviour, road conditions, weather, location, and other factors is too complex to track at such a scale.
By testing in a laboratory, important variables can be set and their values easily tracked. Furthermore, vehicles from model year 2015 and later must complete a five-cycle test for fuel consumption in Canada. The previous testing procedure included only two cycles.
These are the five cycles test vehicles must now complete to receive their fuel-consumption ratings:
- city driving
- highway/rural road driving
- air conditioner on
- driving in cold temperatures
- faster driving with more rapid acceleration and braking
So, what do the values on your EV’s range indicator mean?
Your EV’s range indicator
The range indicator—also sometimes called a range display—operates similar to a fuel gauge on an ICE vehicle. However, instead of showing just one value, it shows two: percentage or kilometres remaining.
The advertised range of your vehicle comes from laboratory testing. The range left on your indicator comes from the past few days of your driving. Because the time range taken into account varies by EV, we’ll talk in generalities here.
If you spent the past few days driving in the city and then venture out on a road trip that uses mainly highway driving, your range indicator may give you more range than you actually have left. That’s because you used more regenerative braking in the city and drove at lower speeds. Higher speeds drain a battery faster, and the reduced braking during highway driving leaves less energy available to recharge your battery.
On the other hand, suppose you take two one-hour highway trips each day and then spend the weekend in the city. The range indicated may show less available power than you actually have.
Which is more accurate: percentage or kilometres remaining?
Currently, neither value is more accurate than the other. When driving on the highway, changing the indicator to show the estimated number of kilometres left will help you gauge when you should pull over to a charging station. Because charging stations aren’t yet as ubiquitous as gas stations, you’ll appreciate the heads-up.
However, when driving in the city, where you use your brakes often, make frequent short trips, and can charge your car in many locations, including home, watching the remaining battery percentage makes more sense.
For more questions on your EV, visit a NAPA AUTOPRO service centre near you.