One of the biggest concerns with electric cars like the Tesla Model S is how quickly the battery will degrade. After all, we've all had a smartphone or laptop that had its battery life nosedive towards the end, so shouldn't that apply to an electric car too?
Yes. And no. With any lithium-ion rechargeable device there will be degradation of the battery over time and repeated charge cycles. But the battery pack in a Tesla EV is quite different than the one in your phone, with a specialized design and chemistry particularly well suited to the demands and rigors of electric vehicles, plus support systems to extend its longevity.
At Plug In America they've been collecting data submissions from hundreds of Tesla owners on the performance and longevity of their car's battery. Using their data, we looked at a selection of fifty Model S cars with more than 50,000 miles on the odometer: original rated range, reported range, and odometer reading.
With a sampling of 60, 85, and 85P battery packs and drivetrains (Plug In America doesn't have any greater-than-50,000-mile data points for the newer dual-motor setups or 70kWh or 90kWh packs), we ran the numbers and found that on average a Tesla owner should expect a loss of around 2.3 miles range for every 10,000 miles driven.
This applied across the board, whether it was a 60kWh pack or an 85kWh pack — it was an across-the-board drop in numerical range, not a percentage from the battery's original capacity. There was some variance in the numbers, as one would expect from results reported by real-life drivers in a wide range of environmental and driving situations — some saw as little as 0.16 miles loss per 10,000, while others saw as high as 5.1 miles per 10,000 driven.
According to the U.S. Department of Transportation, the average driver in the United States puts 13,476 on their personal vehicle, which works out to about 3 miles per year in decreased range — it would take the average owner of a 215-mile-range Tesla Model 3 more than five years to dip that range under the 200-mile mark.
Tesla takes a number of steps to preserve as much of the capacity of their batteries as possible. Aside from the aforementioned chemistry and architecture, Tesla cars are also equipped with active liquid cooling to ensure the battery pack doesn't overheat and when charging towards maximum capacity the charge rate dramatically slows to avoid overcharging, both of which would impact range. Tesla also sets the default daily charge limit to 90% and only recommends charging to 100% when you're planning a long trip. They also advise drivers not to frequently deplete the battery if it can be avoided to extend its useful life.
The warranty that Tesla provides for battery packs covers any faults in the drive unit and battery pack for eight years and infinity miles, though that does not cover within-bounds range degradation due to everyday driving. Then again, after eight years the average Tesla would have lost only around 25 miles off the rated range.
Tesla's battery-powered cars aren't alone in the world of decreasing efficiency. Internal combustion cars also have to contend with decreased mile-per-gallon efficiency over their lifetimes from component wear to deposit build-up — and that's even with thorough maintenance of their highly-complex drivetrains.
So, yes, a Tesla or any other EV will see the range its battery pack can provide decrease over time. But it's nowhere near as bad as the fear-mongering or your intuition might lead you to believe.