Battery capacity (and range) degradation over time or distance traveled is one of the several main concerns in terms of electric cars. About 10 years ago, no one really knew how those new EVs would cope and some models were clearly underperforming (for various reasons).
Today, we will take a look at the official data from Tesla, which is extremely valuable because the company already has the most experience (in terms of the number of all-electric cars sold globally).
Tesla says that its battery packs were designed to outlast the cars. The average usage of private passenger cars (ICE) in the U.S. is 17 years and roughly 200,000 miles (322,000 km). The mileage in Europe is lower - about 130,000 miles (209,000 km). So, we have the first indication that the batteries should last longer than that.
Battery capacity is above 85% (on average) after 150,000-200,000 mile
After selling more than 1 million electric cars, Tesla's battery degradation data shows that vehicles with mileage between 150,000-200,000 miles (241,000-322,000 km), on average, still have more than 85% of initial battery capacity (the battery degradation is below 15%).
Model S/X data
Most of the Tesla cars are very young (more than half are less than 3-years old), so the company provided a chart with battery capacity retention per distance traveled for the Model S (produced since 2012) and Model X (produced since 2015).
We noted several things:
- the initial battery capacity fade is higher in the beginning and then stabilizes at a slower rate
- we estimate (from the chart) that the first 5% of battery capacity is gone (on average) after about 25,000 miles (40,000 km)
- another 5% (total of 10%) is gone (on average) around 125,000-150,000 miles (200,000-241,000 km), but it's difficult to estimate because the curve is really flat
- after 200,000 miles (322,000 km), on average, the capacity degradation is below 15% (the car still has more than 85% of the capacity and corresponding range)
- the lowest capacity within the standard deviation (see wiki) is noticeably above 80% after the 200,000 miles (322,000 km), but there might be cases worse than that (the population of those cases might be 10-20% we guess)
- there is a higher variation in the high mileage results (150,000-200,000 miles) as there are simply fewer cases and some might be very specific.
Assuming that Tesla's new cars and new battery designs (in Model 3/Model Y) are improved compared to the older types in the first S/X, and the overall goal is to move towards 1 million mile batteries, we expect that the results will be even better in new Teslas.
In old electric cars, in which batteries are still performing well, the pack might be repurposed for other EVs, other DIY projects, energy storage systems and ultimately recycled.