You may notice that certain vehicles seem to have a lot of variability in the range they can get at 100% charge. One car will only achieve a range of 133 miles, while a different car of the same exact type can see a range of 325 miles. What’s going on here, and where is your used car likely to fall in terms of range expectation?
To illustrate that point, here's a screenshot from one of our vehicle guides.
How does Recurrent calculate the range at 100% charge?
When Recurrent gets data from a car, we get a few pieces of information directly from vehicle telematics: odometer, state of charge, on-board range estimate, and external temperature. If we observe your car at 65% state of charge, we use the other data to extrapolate what your range would be if you were at 100% in the same conditions.
The easiest explanation for why our range predictions are not the same for every single BMW i3 (or Tesla, or Volt…) is because there is natural range degradation that happens over time. A car that is a few months, or a few years older than another may see slightly degraded range estimates. This does not necessarily mean that a newer car is always better, since the way a car is used matters a lot, but age-related range loss will always be a factor. If you’re looking at a bunch of cars and there is a wide “range of ranges,” remember to check if the vehicles span model years.
Another thing that we know will affect short term range predictions is temperature. If it’s very cold or very hot, your car may predict a range up to 30% less than expected. Recurrent has written a lot about the temperature effects on range, but in short, it is usually a temporary effect and your range will return when it’s between 60-80 degrees. You can assume that the low end of vehicle range predictions is for cars in extreme temperatures.
Terrain and driving conditions - whether hilly, stop-and-go traffic, or with a car full of heavy suitcases - will also affect the range prediction. It is not very well studied how much of an impact these specific factors have on the range, but with EV pickups on the horizon, people are beginning to study the effects of towing. One thing we are sure about is that cars driven mostly on the highway predict lower ranges than those driven in cities and around town, thanks to the effect of regenerative braking. And, without a doubt, all these effects vary between car makers.
Since we are using the range estimate from your car to extrapolate the range estimate at full charge, any of the biases or calculations that your car makes to get that number will factor into our predictions. This means, for instance, that Teslas will show very little variation based on the weather, since their on-board systems hide the way range fluctuated with extreme temps. On the other end of the spectrum, Chevys are very sensitive to temperature changes and may overreport range loss in extremes.
Finally, like with anything, there are natural variations between individual cars, even those of the same year make and model. The exact way that certain components line up and fit together may vary minutely from car to car, meaning that one Model 3 will always get a few miles less than another one across town.
If you want to learn more about long term battery degradation, we wrote an e-book to help people understand it. It's free for download.