There has been some really interesting battery range degradation happening with my 2021 LR Model Y over the past month, so I though I would put a blog together this weekend to explain what I am seeing and my thoughts on the matter. I have now owned my Tesla for 2 years, 3 months and have racked up nearly 43,000 miles on it (I will pass 43,000 on our way home on Sunday for sure).
The first item to address is the Tesla range calculation vs. the GOM (aka Guess-O-Meter) used by other EV manufacturers. The numbers I am going to be talking about in this blog pertain to the estimated range that is reported by the car on the main display and not in the trip display. The trip display uses recent driving history to predict remaining range while the main display of range is based, I presume, based on the % of charge left of your estimated battery capacity with degradation, times some mile/kWh factor based on EPA sort of numbers. For this reason, when a Tesla owner charges up to a consistent %, the reported range a Tesla owner will see will mostly remain unchanged with slow reductions over time. Many other EV brands display the equivalent of the Tesla trip range value.
At the end of the day, neither of these different type of GOM values in the display are not all that useful for determining how far you can actually drive with the % of Battery you have left. There are just too many other factors like weather, elevation change, and speed that will all have an impact. For this reason, it really doesn't matter for most Tesla drivers if your vehicle has any degradation as you just trust what the in-car navigation says and estimates it will need for the next leg of your journey, and all will be fine.
I use a service called TeslaFi (.com) which pulls data from my Tesla account about my vehicle. The data their system reports as the range of my vehicle has been basically identical to that reported in the car, so for the rest of this blog, we'll assume the TeslaFi data is accurate.
The graphic below (from TeslaFi.com) shows the average fleet degradation for other Model Y LR models. First, if you focus on the Green trend line, you'll see a fairly steep degradation curve from 0 to 20,000 miles. About 6-7% on average. From 20,000-35,000 miles, the degradation begins to slow down a good bit, and then beyond 35,000 miles, the degradation is minimal at less than 1% per 10,000 miles.
Before I get into the reported range of my car, I want to talk about what this means for the average Model Y owner. Assuming 0.5% to 1% degradation for the rest of the life of this vehicle, by the time a Modely Y LR reaches 200,000 miles, it will likely still have 265 to 285 miles of usable range. Out to 300,000 miles, 235-270 miles of range. What is the actual impact to an owner of a vehicle that has reduced range?
Long Trips - surprisingly, almost 0 impact. Using a web service called ABRP.com, the travel time to get from SE PA to Disney World in Florida, a 15.5 hour drive + 2 hours of charging ends up being about 5 minutes longer in a vehicle with 270 miles of range vs. 300 miles of range.
Short Trips - sort of depends on a couple of factors. First, only if the trip was right at the edge of your previous range, and you were forced to stop to charge along the way, then you are probably adding 10 minutes or less to a trip that is 2.5-3 hours long. If it is a trip like the one we take to the Finger Lakes, we stop on the way in Ithaca no matter what to have a high SOC entering the area. This might only need an extra 5-10 minutes of charging as well to add a few more %.
Local Driving and Commuting - absolutely zero impact.
So basically this reduction in range after 200,000 miles would have zero impact to the daily life of the EV owner, and even on long road trips, the owner wouldn't even notice. Given that I am looking at another 8-10 years until I see this sort of reduction in range, we should also see a proliferation of charging infrastructure improvements across the country.
I am actually surprised by the long trip analysis I did above. I really thought it would have much more of an impact. This sort of makes a case for not over buying a car with longer range when one with 250-300 miles would actually work perfectly fine. The one case against this argument is that there are still areas about the country that don't have chargers on long stretches of highway.
I am at least 4-5 years away from hitting 120,000 miles and 8-10 years from 200,000 miles. I have never owned a car past 120,000 miles as traditional ICE cars often start to have maintenance issues, and ownership becomes either a hassle, or the vehicle just becomes an unreliable form of transportation. Vehicle reliability was a critical driver when our kids were young and we didn't have a spare vehicle. A busted vehicle would be nearly unbearable in the days when we were both working and hauling kids all over. Fast forward to today and definitlly 10 years into the future and we barely need two cars as it is (we often commute with one another) and we actually have a 3rd vehicle as a spare right now if we really needed one. Will we keep the Model Y until 150-200k miles? Maybe. Probably depends on when I have a chance to purchase a CyberTruck or an Aptera.
So let's talk about the Degradation estimate on my particular vehicle (the Blue line). The first thing to note is that the data is very "noisy". There is no real smoothness to it at all. It can vary by up to a mile day to day, and in some cases, there are huge reductions and even gains that have occurred over time. For the most part, my car is following the trend of the average Model Y. My vehicle was actually reporting a max range of 330 miles when I first purchased it even though Tesla advertises 326 for my version of the Model Y.
At about 35,000 miles, I started a several month long experiment to see if my charging habits had any impact on my battery degradation. I daily charged to 80% then 90% before returning to my previous routine (at about 40,000 miles), which was charging up to 90% whenever I "needed to", which there was no science to. I would think about how much charge I needed the next day, added 10%, and if got home with less than that SOC, I would plug in (usually 30% or so was the threshold). Did this have any impact? I don't think so. Sure, it sort of reduced the daily variations and as a result, may have resulted in the little bit of increase that I saw during this period of time. I have done short stretches of returning to daily charging for a week or so and have not been able to see any sort of similar results. It just fluctuates and changes over time and EV owners just need to accept this.
The data below nearly covers the last 10,000 miles of driving. The first half of this data was my "experiment" with daily charging. Since then, I have returned to my more random charging approach. What is interesting to note is that during most of this time, TeslaFi was reporting my range was roughly better than 60 - 75% of other Model Y owners. In the last month, I have experienced yet another sudden drop in range which now puts me below 75% of the other Model Y owners. Am I concerned? No, but it is something I am going to look at closely. You can see that over the last 7,000 miles, I have received 9 different SW updates to my vehicle. It is possible that any one of these updates may contribute to what I am experiencing. I had an opportunity last night to run a HV battery diagnostic check last night. More on that below this graphic.
HV Battery Diagnostic - The process is quite simple and there are plenty of videos out there on YouTube to show you how to perform this test. I started the process with 28%. The vehicle immediate had the HVAC system on full power (not inside) pumping heat out around the outside of the car to burn down the SOC in the battery. It was able to drop the power by about 1% every 5 minutes until it got to 6% or so where it seems to shut everything off and slowly walk it down for another hour or so down to 5%. Once it hit this level SOC for awhile, it bagan the process of charging the vehicle up to 100% overnight.
Results... well, I was hoping that I would see an slight increase in the reported range as a result of this process being able to calibrate the BMS a bit better. In reality, I lost another 1.5 miles according this their report and I am now right at 300 miles of range (just under 10% degradation since purchase). The report on the screen (below) is also saying I have 88% battery health. That would mean 340 miles of range at 100% health. I am not sure how to interpret the number from this test really. I never ran the test when I first owned it. Did it have 97% health thus 330 miles when new? Such that my current degradation since then is closer to 9% additional? Not sure. The big take away from all of this is that I feel like I can really trust the data I am seeing in TeslaFi and that running this process systemically results in a BMS calibration.
