EV Battery Degradation Just Isn’t Much Of An Issue

• A new video from RSEV shows why you shouldn’t worry about your EV’s battery.
• While EV batteries do degrade, it happens so slowly that the battery will likely outlast the car.
• Even if you do see some degradation over 200,000 miles, battery failure is extremely unlikely in a modern EV.

RSEV analyzed the battery health of 300 medium- and high-mileage EVs, and the results confirm what we already knew: You really don’t have to worry about your EV’s battery.

On average, cars retained 90% of their battery capacity for 90,000 miles. That’s already impressive. But consider, too, that battery degradation is the strongest within the first couple of years. That means that a car with 130,000 miles on it retained 85% of its initial battery capacity. That means we’ve seen plenty of examples of cars getting past 200,000 and even 300,000 miles with 80% capacity or more.

The good news doesn’t stop there.

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First, look at this chart to get an idea of the degradation curve: 

If it looks steep, let’s zoom out so that the chart starts at 0%, rather than 80%: 

It’s damned near a straight line.

Then consider that most cars sold these days have an unusable “buffer zone” that’s hidden to the user at first. As the battery degrades, the buffer zone gets tapped to replace lost capacity. That means that while the actual pack’s range may have degraded, the usable range can stay the same through 100,000 or 150,000 miles.  

More good news: These charts seem to represent a worst-case scenario, due to the data set. RSEV is a used EV dealer in the U.K., and its analysis covers cars that are coming off a lease. Leasing works differently in the U.K. and is common for company cars, but the terms are still usually three or four years. That means that not only are these cars doing 90,000 or 130,000 miles, but they’re doing that high mileage in an exceedingly short time. Most cars will take a decade to hit that number, especially in the U.K., where the average driver doesn’t cover as much ground as they do in the States.

That means these cars were driven hard, year round, and must have relied on relatively consistent DC fast charging. They’re also 2021 or 2022 models, and both battery pack quality and overall EV reliability has improved significantly since then. Just look at the Jaguar I-Paces in the data set. That product was on sale in 2018 and represents an earlier generation of battery production and management tech, and as a result has the worst performance in the set.

One more bit of good news, then I promise I’ll stop: Even when EV batteries degrade, modern ones almost never fail. That means that while your 200,000-mile Tesla may have only 80-85% of its original range—remember, degradation slows down after the first year—it will almost always still work. That’s in contrast to an internal combustion engine, which often works right up until the instant it doesn’t. Sure, a Model 3 Long Range with 290 miles of range is less useful than a new one with 363 miles of range. But it’s still useful enough to be your only car, and its slow rate of degradation means you could keep driving it for years. It’s not like the motor will fail, either.

Forgive my excitement here. But I’m a reliability nerd, and the biggest thing I was worried about with the EV transition was that these cars would become disposable consumer electronics devices with factory-implemented expiration dates. I hate how quickly smartphones become E-Waste, and I hate how many automakers try to stop consumers from fixing their vehicles themselves.  

Yet I no longer worry about that at all. Tesla has opened up their diagnostic software to consumers. Its batteries often last 300,000 miles or more. Its motors no longer have major issues. It has delivered on the promise of EV reliability: A simpler vehicle means there are fewer parts to refine, which means a more reliable vehicle. This isn’t immediate, as EVs are new technology. Many automakers are still in their “making mistakes and learning from them” era, not their mature technology era.

Cross this valley, though, and there’s a golden meadow on the other side. One where not just Toyotas, Hondas and American trucks are 250,000-mile vehicles, but where any company with half-decent tech can make them. Your infotainment bugs and window regulator issues will likely persist into the new era if you buy a Mercedes or what have you, but worrying about a 150,000-mile powertrain will soon be a thing of the past. 

Contact the author: Mack.hogan@insideevs.com.