How long does a Tesla battery last? My Tesla is losing range!

One of the most common claims I get in my EV and Tesla videos is about

battery

long

evity. Statements like "you will have to replace the

battery

in 5 years." Or “replacing it will cost you $10,000 in a few years. There go the 'savings' for driving an electric vehicle.” And from EV owners I hear questions like: “I've lost 8 miles of my car's rated

range

. Should I be worried?" Well, I've teamed up with the developer of the fantastic iOS app, Stats, to take a look at some real-world data and see if we can address those concerns when it comes to Model 3.

I'm Matt Ferrell. .. welcome to Undecided So, first things first, let's address the statement you often hear: “replacing your battery will cost you thousands of dollars in a few years. This statement sounds like it would be true. something like a smartphone that won't charge after a couple of years. Or a laptop that you can't use for more than what seems like a few minutes before having to plug it back in to charge it. A phone has a lithium ion battery. Lithium. An electric vehicle has a lithium-ion battery. So it must be true that an electric vehicle's battery will be virtually worthless after a few years, just like the one in your smartphone.

The problem is that correlation

does

not imply causation. Humans are natural pattern recognition machines, so we are prone to finding perceived connections between things when that connection

does

n't actually exist... or in this case... it's simply misunderstood. I have posted several videos about battery technology and research that is currently being carried out. I'll include some links in the description if you're interested in seeing more, but there are some pretty big differences between your phone battery and an electric vehicle battery. The first big difference is the number of batteries we are talking about. You have a single lithium-ion battery in your smartphone.

An electric vehicle is made up of many small batteries joined together into a single battery pack. A standard

range

Tesla Model 3 battery backup has 2,976 individual cells in the battery pack. A

long

range battery pack is made up of 4,416 individual cells lined up in rows with a sophisticated battery management system, which controls charge, discharge and temperatures. The system manages individual cells to maximize their efficiency and longevity, so degradation that occurs over time is carefully controlled. It's very different than a single cell on a smartphone. The second big difference is the charging behavior. How many of you plug your phone in at night when you go to bed and then unplug it in the morning when you wake up and go to work?

And then do you sometimes plug in your phone at work or while riding in the car? Lithium-ion batteries work best when used at 30% to 70% of their charge. It's harder on a battery when you drain it to zero and charge it to 100%. Therefore, constantly bringing your phone's battery to 100% over and over again, as well as leaving it plugged in at 100% for extended periods, will actually accelerate battery degradation. Manufacturers have been implementing battery management systems to help combat this, such as in Apple's iOS 13 update. The system learns over time when you usually get up in the morning. It will charge your iPhone to 80% overnight and wait for it to trickle charge to 100% shortly before you normally wake up.

Systems like this can help reduce battery loading and improve battery life. Electric vehicles, like the Tesla Model 3, also recommend a daily charging amount. When you plug in your car, the Tesla user interface will show you the recommended range for daily charging and will also make it clear that exceeding 90% should only be done for longer trips. As soon as you reach 100%, you will need to start your journey immediately. Keeping your daily charging routine below 90% helps maintain good battery health. Below are some results from a study that showed how charging behavior affects the longevity of lithium-ion batteries. The Y axis represents the total available charging capacity and the X axis represents the number of charging cycles.

Batteries that were charged to 100% and depleted to various states of charge performed worse than batteries that were charged to 75% or 85% before being depleted. To be very clear, let's compare two data points on the graph. Both used 50% of the battery capacity for each cycle, but one was charged to 100% and the other to 75%. After 1000 cycles, 100% of the battery was reduced to just over 90% of its original capacity. Widen that and the gap will widen after thousands of charge cycles. And finally, an electric vehicle's battery pack typically has a shock absorber built into the top and bottom ends of the battery.

That means the car's 100% display is probably not the actual 100% battery. The same to drain it to 0%. There is leeway in the battery to maintain the car's electrical systems if the battery gets too low. This buffer gives the car's battery management system some leeway in estimating the vehicle's total range. In some cases, you can consume that buffer slowly over time so that the car's driving range appears unchanged. It's unclear if or to what extent Tesla is doing this, but there may be some wiggle room there. What all of this shows is that you can't equate your phone's battery life with what you can expect from your car's battery life.

So let's look at some data that Ramin, who is the developer of Stats, collected to see how the Tesla Model 3 batteries are holding up. By looking at around 15,000 stats battery range data points, you can see some pretty clear trends. that are taking shape. If we look at the average range reported for the long-range rear-drive Model 3, you can see a rapid decrease in range over the first 15,000 miles and then it starts to level off a bit. This fits with what we've seen with the Model S, which also slows down degradation as more miles are racked up. It is a non-linear form of degradation.

If we say the average driver drives about 12,000 miles a year, that could go from 324 miles to 313 miles, or a 3.4% drop in range in the first year. The second year goes from approximately 313 to 308, which represents only a 1.6% drop for the following year. Model 3 Long Range AWD shows similar drops; going from 310 to 301 in the first 12,000 miles, which represents a drop of approximately 2.9%. And like the rear-drive Model 3, the AWD's next 12,000 miles decrease by 1.6%. Tesla warranties its long-range batteries for 8 years, or 120,000 miles, at 70% of the original charge. That means a long range, AWD, 310 mile battery could have a range of around 217 miles after 8 years in the worst case scenario.

If you break that figure down into a year-over-year degradation rate, you could see a loss of 11.6 miles per year. But as you can see from the data, Tesla, like any other company's warranty, is based on the worst case scenario... and how much you drive. A driver who drives 12,000 miles a year might see an 11-mile decrease in the long-range rear-drive Model 3 in year 1, but only a 5-mile drop the following year. Long-term degradation should, if it follows what we've been seeing in the Model S and We can also take a look at the data in a broader view to see the full extent of the ranges reported per 1,000 miles driven.

If you have never seen a violin plot before, this will help illustrate the spread and concentrations within each group. Each curve is essentially a small bell-shaped curve on its side. Most people will fall in the middle of the curve, where it is highest, which is also where the median falls. The lowest points on the curve are the outliers, which are less common, but may still be experienced by some of you. In fact, I myself am one of those outliers in this data. There's a lot to take in when looking at this type of view, but there was something that caught my attention about the layout.

There are a lot of fluctuations in the nominal range in the spread from one group to another, but there is one big drawback to remember with the nominal range: it is an estimate. And that estimate, which is generated by the battery management system, can be out of calibration with the actual maximum capacity of the battery packs. If you charge at 80% every day, there may be a small variation in that estimate, which can be rebalanced by charging at 90% or maximum for a long trip every now and then. Software updates sent to your car can reset some of those estimates, which can also contribute to sometimes seeing them fluctuate up or down.

I have seen this myself. After v10 was released, my rated range started going up again. Charging and driving habits, such as not charging every day or driving every day, can cause the degradation numbers to appear high, even if the battery's health is good. Ramin recently launched a new app, where you can enter your rated range, current charge percentage, and odometer to see where your car sits within the data I shared in the video. Looking at my car, I'm outside the norm, on the lower end, for cars that match my criteria. I'm keeping an eye on it, but I'm not worried.

As EV owners, we need to look beyond the small fluctuations we may see in our rated range and keep an eye on the long-term picture. Follow best charging and usage practices, such as charging to 80% or 90% each day. Only charge to 100% for longer trips and start driving as close to 100% as possible. As I showed in the data, when you look long term, you should see something smaller like a 4-5% drop in the first 24,000 miles. Electric vehicles are still relatively new to many people, so there is a lot of fear, uncertainty and doubt. It's easy to jump to conclusions based on limited experiences and believe some of the misinformation out there.

But even EV owners like me can get caught up in range anxiety and be hyper-vigilant in keeping track of our battery's rated range estimates. Any small fall can make us worry and worry about how long our car will

last

. In the end, my conclusion after looking at these numbers and doing some research: just relax and enjoy the car. So where do you fall on the EV driver spectrum? Worried about battery degradation or not worried about all this and just enjoying the car? Or a little of both? I've never really cared about mine, but I do get a little obsessed with numbers and data, so I've been following mine closely more out of curiosity than anything else.

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