I thought I would use this blog post to set the record straight when it comes to EV battery life and degradation. I saw a post on Twitter recently that indicated that the general public believes EV batteries must be replaced every 75,000 miles. I am hear to tell you that is not the case at all. Sure, there are some situations where batteries fail prematurely, but for the most part, today's modern EV batteries will last for well over 360,000 miles. I actually did a full analysis in blog post #25 here.
So, after 50,000 miles, let's take a look at my 2021 Model Y battery degradation. The plot below comes from TeslaFi (.com). The Green line is the average of all Tesla Model Y vehicles with similar miles on the vehicle at the time of charging, and the Blue line is my Model Y reported maximum range at 100%. The first thing you should notice is that the first year to year to 18 months of ownership out to about 30,000 miles driven, the Model Y fleet average drops "significantly". In this case, the average Tesla Model Y experienced about 6% of degradation. This is the common experience of almost every EV owner. The first year is when the most battery degradation is going to happen. After the first year, you then see that the degradation curve almost completely flattens out. In fact, the fleet average lost less than 1% over the next year! That is frankly amazing. That means after a total of about 12 years of ownership, most Model Y's will likely have over 270 miles of range at 100%. There are tons of brand new vehicles that are being produced right now that START at less than 270.
Now let's take a look at my individual experience (the Blue line). The first thing that you should see is that my data isn't smooth. It goes up, it goes down, and even when it seems to be sort of flat, it is still highly variable day to day. Why? Well, I am no battery expert, but measuring the capacity of a battery is really hard to do. It requires measuring Voltages and currents, sometimes under load. To make it even harder, these things change as the temperatures of the battery cells fluctuate, and under driving and charging conditions, the battery pack can have a wide range of temperatures across all the different cells in the pack. Basically, it really isn't an exact science.
For most of my ownership experience, my vehicle has had slightly more capacity than other vehicles of similar mileage. For reasons I cannot explain, my battery showed a rapid reduction in capacity starting in August that conditnued through the end of December. I believe I posted about this last fall and that I was watching it closely. Since the start of the new year though, I have now seen a steady increase in my battery capacity, again, for reasons I cannot explain. My theory is that just might have been some cells that were not getting charge balanced, and as such, the total pack capacity wasn't reduced a little. Now, for some reason, maybe some of those cells are balancing better resulting in an increase in my pack capacity. My own experience is that after the initial 5-6% battery degradation, I am seeing about a 2%/year reduction in my battery capacity. We'll see if this continues (to increase) and if my overall experience is a flattening closer to 1%. If you project a 2% degradation out to 12 years of total ownership, I'll be looking at about 245 miles of range at that point, which honestly, will be plenty of range for 99% of the driving I'll be doing with this vehicle by then. I'll also have over 200,000 miles on the car by then if I even still own it (I have never owned a car past about 120,000 miles, so we'll see).
Basically, I am not concerned at all about my vehicle's battery at this point. It just varies day to day and it will have trends where it will drop and increase range, but I am expecting a this point, I'll see 1-2% degradation from here on out and that is fine by me.
Here is the thing that people need to realize. If you plan out a trip using ABRP assuming a 9% degraded battery vs. one that is 23% degraded that is from Philly to the Magic Kingdom (over 1000 miles), the trip is still easily possible with the degraded vehicle, and, it only adds 35 minutes to the entire trip, likely less if you assume one of the stops would be overnight at a hotel that has on-site charging.
Here is a closeup of the more recent battery range data (since Jan 1, 2023):
Thanks again for reading! If you are interested in buying Tesla products, please use my referral link to buy a Tesla and get awards like 6 months of Free Supercharging and 3 months of Full Self-Driving Capability.