The Tesla S came out 5 years 3 weeks ago, for reference.
If Tesla has managed to make magical batteries that don't degrade, where no other company has managed it, I want them making batteries for all my devices. Every single Li-ion battery powered device I've ever owned has shown significant battery capacity loss inside 3 years. My laptop is about 4.5 years old and has 55% remaining battery capacity. My old iPhone 4S, which is a little under 5 years old, has like 25% original capacity. I can throw out a dozen examples of Li-ion battery packs that definitely did degrade with use, but none that magically only degraded a tiny amount, or--as some Tesla maniacs claim--got better with age.
If people are getting their reported battery capacity from the car itself, that means nothing at all. The only way to really know the battery pack capacity is to run the car almost dry along the same route periodically, see how far you got, and see how it changes over time. Not too many people are doing that (none, in fact, that I've found have actually done that obvious test). If you only drive 60 miles a day, and your battery goes from 300 miles of ideal capacity to 180 miles, you won't even notice the difference until that one time you need to make a long trip.
Since it's such a PR issue, it would also be trivially easy for Tesla to fudge the numbers. Even for real-world testing. The obvious way of doing it is simply overprovisioning the original battery pack--give it more capacity than it needs for the base range--then artificially limiting range. Maybe the original pack has 400 miles of real range, but they only let it run 250-300. Then over time, as mileage increases, let the battery discharge to a lower point as the capacity drops. Net result = no apparent change in capacity over the first several years, even though there was actually a significant drop.
Some EV/hybrids are built with an overprovisioned battery for sure. It's a known technique. Many good SSDs work the same way; they have a whole block of spare cells to replace worn cells as the drive ages. Perception that the expensive device is long-lived and durable is much more important than absolute base capacity.
But that game only goes so far, and eventually the battery will start to show its degradation at the real rate. For people who buy vehicles expecting to drive them into the ground, that's a serious problem. But if you only keep your vehicles for 5-7 years you're not going to care.
If Tesla has managed to make magical batteries that don't degrade, where no other company has managed it, I want them making batteries for all my devices. Every single Li-ion battery powered device I've ever owned has shown significant battery capacity loss inside 3 years. My laptop is about 4.5 years old and has 55% remaining battery capacity. My old iPhone 4S, which is a little under 5 years old, has like 25% original capacity. I can throw out a dozen examples of Li-ion battery packs that definitely did degrade with use, but none that magically only degraded a tiny amount, or--as some Tesla maniacs claim--got better with age.
If people are getting their reported battery capacity from the car itself, that means nothing at all. The only way to really know the battery pack capacity is to run the car almost dry along the same route periodically, see how far you got, and see how it changes over time. Not too many people are doing that (none, in fact, that I've found have actually done that obvious test). If you only drive 60 miles a day, and your battery goes from 300 miles of ideal capacity to 180 miles, you won't even notice the difference until that one time you need to make a long trip.
Since it's such a PR issue, it would also be trivially easy for Tesla to fudge the numbers. Even for real-world testing. The obvious way of doing it is simply overprovisioning the original battery pack--give it more capacity than it needs for the base range--then artificially limiting range. Maybe the original pack has 400 miles of real range, but they only let it run 250-300. Then over time, as mileage increases, let the battery discharge to a lower point as the capacity drops. Net result = no apparent change in capacity over the first several years, even though there was actually a significant drop.
Some EV/hybrids are built with an overprovisioned battery for sure. It's a known technique. Many good SSDs work the same way; they have a whole block of spare cells to replace worn cells as the drive ages. Perception that the expensive device is long-lived and durable is much more important than absolute base capacity.
But that game only goes so far, and eventually the battery will start to show its degradation at the real rate. For people who buy vehicles expecting to drive them into the ground, that's a serious problem. But if you only keep your vehicles for 5-7 years you're not going to care.