Most of us have grown up with cars powered by internal combustion engines. They are remarkable feats of engineering, derived from decades of automotive experience and advancement. Modern cars are extremely reliable and need only minimal maintenance. We expect them to get us to work or our travel destinations without incident, and we expect them to last for a decade or more.
Electric vehicles, on the other hand, are unfamiliar to most of us. We have lots of other machines powered by electric motors, like our refrigerators, washing machines, and ceiling fans, and we generally assume they are reliable and free of maintenance. But our experience with the electric machines powered by rechargeable batteries is more limited, and different. For example, we expect we might need to replace the batteries in our cordless electric drills every few years.
Most of us equate lithium-ion batteries—the miracles of modern chemistry powering our cordless electric devices, including EVs—to the ones in our iPhones.
Most of us equate lithium-ion batteries—the miracles of modern chemistry powering our cordless electric devices, including EVs—to the ones in our iPhones. Many people experience significant loss of battery capacity in their cell phones after two or three years. Time to buy a new iPhone! Not so bad because that new iPhone is better anyway—faster and with a sharper display and a better camera. And it’s not that expensive to buy a new phone every few years.
But an electric car with rechargeable lithium-ion batteries? Many people think they’ll have to replace the battery after a few years—at a cost of thousands of dollars. No thanks! They’ll stick with their gas car, which they know will last for many years.
So how long do batteries in electric cars last?
If you’re considering joining the transition to electric vehicles, should you really be worried about a big bill a few years down the road to replace the car’s battery pack? And with EVs so new on the scene, isn’t this a risky proposition?
Electric vehicles have been on the roads for about a decade now, and there are lots of them at this point, many with more than 100,000 miles. So we have some real-world data on EV battery degradation. And it looks pretty good.
Actually, electric vehicles have been on the roads for about a decade now, and there are lots of them at this point, many with lots of miles. So we have some real-world data on EV battery degradation. And it looks pretty good.
The first point to understand is that battery chemistry is a complicated engineering problem, with tradeoffs between power, energy density, and longevity, as well as other factors like safety. So the design tradeoffs in your iPhone battery are different than those for an EV battery pack, resulting in different chemistries. An electric car battery is not like the one in your iPhone.
The battery in an electric car is not like the one in your iPhone.
Also, good engineering matters for batteries, just like everything else. The batteries in early-model Nissan Leafs had serious problems in extreme heat—like parking lots in Arizona—and Nissan had to replace a bunch of them. But that was a result of design decisions Nissan had made, both in the battery chemistry and the battery pack cooling system. Other automakers, like Tesla, made different—better—decisions on those important engineering details.
What Do the Data Say?
At this point, we probably have the best data on Tesla Model S and Model X batteries. Many of those vehicles have been on the road for almost a decade, and there are lots of them. And because they are long-range vehicles, they have accumulated lots of driving miles.
Data on battery gradation show that capacity drops by single digits in the first years and then levels off.
Data on battery gradation show that capacity drops by single digits in the first years and then levels off. More specifically, battery capacity can be expected to drop by as much as 5 percent initially, with capacity remaining at 90 percent after 150,000 miles and 85 percent after 200,000 miles. Those kinds of numbers result in a useful vehicle with longevity on par with a gasoline-powered car. And over a similar period, that gas car is going to need a lot more major maintenance on its power train.
This picture is basically the same for both data released by Tesla (first chart) and wiki data collected from Tesla Model S and X owners (second chart).
Warranties cover the most serious degradation cases.
Of course, there are outliers in the data, with some vehicles experiencing somewhat more degradation. Tesla’s warranty covers the most serious degradation cases. For example, my Model Y is warrantied for 70 percent retention of battery capacity for eight years or 120,000 miles. Other EV makers offer similar warranty protection.
Battery longevity is expected to continue to improve in the coming years as chemistries advance. Tesla has talked about eventually achieving what it calls a “million mile” battery pack to go with the million miles it estimates that its electric drive trains will last.
How You Charge Can Affect Battery Longevity
Owners have some control over the longevity of the batteries in their vehicles, as charging practices have an impact over time.
To improve battery longevity, the basic idea is to refrain from fully charging the battery unless needed for a trip and to avoid fully draining the battery. The rule of thumb is to keep the battery between about 20-80 percent most of the time.
To improve battery longevity, the basic idea is to refrain from fully charging the battery unless needed for a trip and to avoid fully draining the battery. Tesla advises its customers to charge to only 80-90 percent of battery capacity in regular daily driving—more than enough range for those trips—and to charge to 100 percent only when needed for a long road trip. It also advises owners to avoid draining the battery below 10-20 percent of capacity—another reason why longer range is useful for road trips.
And coming back to our first electric car—our trusty eight-year-old Nissan Leaf with 57,000 miles—it still shows all its battery capacity bars on the dashboard display and an estimated range nearly the same as when it was new. A robust sample size of one, admittedly, but some additional reassurance that electric car batteries are not like iPhones.
In short, batteries in electric vehicles can be expected to deliver longevity on par with the lifetime of gasoline-powered cars.
In short, although there have been some exceptions—typically addressed under warranty—batteries in electric vehicles can be expected to deliver longevity on par with the lifetime of gasoline-powered cars. There is little or no risk that the cost of transitioning to an electric car will include the need for a battery pack replacement during the life of the vehicle.