EV Battery Degradation: Do Most Used EVs Retain Over 90% Health?
For years, one of the most persistent myths surrounding electric vehicles (EVs) has been the fear of rapid battery degradation. Critics have long argued that EV batteries lose capacity quickly and would require costly replacements within a few years — making electric cars a risky investment, especially on the used market. But a new large-scale study from Sweden has delivered a decisive blow to that misconception.
The Swedish used-car marketplace Kvdbil has conducted an extensive analysis of the State of Health (SoH) of over 1,300 used EVs and plug-in hybrids.
Their findings? The overwhelming majority of these vehicles still retain nearly all their original battery capacity — proving that modern EV batteries are far more robust than skeptics have claimed.
The Study: Over 1,300 Used EVs Put to the Test
Kvdbil’s study covered 1,366 used vehicles in total, including 723 all-electric cars and 643 plug-in hybrids. The test focused on determining the “State of Health” (SoH) of each battery — a metric representing how much usable capacity remains compared to when the battery was new.
The results were nothing short of impressive:
- 8 out of 10 used EVs retained at least 90% of their original battery capacity.
- Battery degradation was found to occur slowly, thanks to advancements in thermal management, smart design, and improved cell chemistry.
While Kvdbil didn’t disclose the average mileage associated with these results, the dataset represents a diverse range of vehicles that had been driven under real-world conditions. In other words, this wasn’t a controlled lab test — it reflects what actual EV owners are experiencing.
Myth Busted: EV Batteries Are Built to Last
Martin Reinholdsson, test manager at Kvdbil, summarized the findings succinctly:
“The degradation of a car battery occurs slowly thanks to advanced technology and smart design, including cooling of the battery cells. This result also disproves the myth that used cars’ batteries wouldn’t last long.”
This statement underscores the key point of the study — modern EV batteries are not fragile. Thanks to sophisticated battery management systems (BMS) and liquid cooling technology, today’s EVs can maintain their performance and range far longer than previously believed.
The Top Performers: Kia, Tesla, and Opel Lead the Pack
When looking at specific models, Kia emerged as the clear standout in the study. The Kia EV6 and Kia e-Niro secured the top two spots for best average battery health. Tesla’s Model Y followed closely in third place, while other notable entries included the Opel Mokka-e, Mazda MX-30, and Audi Q4 e-tron.
Here’s the Top 10 EVs with the Best Average Battery Health:
- Kia EV6
- Kia e-Niro
- Tesla Model Y
- Opel Mokka-e
- Mazda MX-30
- Audi Q4 e-tron
- Fiat 500e
- Volvo XC40 Recharge
- Citroën e-C4
- Volkswagen ID.4
When brands were ranked by overall battery health (across all models), Kia again led the way, followed by Audi and Opel, with Tesla taking a solid fourth place.
However, as Reinholdsson pointed out, battery health isn’t solely determined by brand or model. Factors such as climate, driving habits, and charging behavior play significant roles in long-term battery performance.
What Really Affects Battery Health
One of the most insightful aspects of Kvdbil’s findings is that battery degradation isn’t primarily a manufacturer issue — it’s a usage issue. According to Reinholdsson:
“It is not really tied to a typical car or typical car manufacturer. It is more to the wear, that is our analysis of it. Age, climate, driving style and charging habits: They play in as fairly large factors on the wear.”
This reinforces what many EV experts have long stated: how you treat the battery matters more than the badge on the hood.
Some best practices to maintain optimal battery health include:
- Avoid frequent fast charging (DC charging) unless necessary.
- Limit daily charging to 80% to reduce long-term cell stress (especially on NMC batteries).
- Avoid deep discharges by not letting the battery frequently drop below 10%.
- Keep the car in moderate temperatures, as extreme cold or heat can accelerate wear.
These simple habits can make a measurable difference in maintaining a battery’s State of Health over time.
The Broader Implications: Confidence for the Used EV Market
The study’s implications extend far beyond technical findings. One of the major concerns for potential EV buyers — especially those considering a used electric car — has been uncertainty about battery longevity. After all, replacing an EV battery can cost thousands of dollars, depending on the model.
But Kvdbil’s research shows that such fears are largely unfounded. If 80% of tested EVs maintain over 90% capacity even after years of use, it suggests that most owners will never need a battery replacement during the typical ownership period.
In fact, the data hints at an even more encouraging trend: batteries might outlast the vehicles themselves. As the rest of the car ages, the battery is likely to remain in excellent condition, ensuring strong resale value and lower total cost of ownership.
A Turning Point for EV Perception
This study arrives at a crucial moment for the global EV transition. While sales of electric vehicles continue to rise, lingering myths about battery life have slowed adoption among more skeptical consumers.
Now, with real-world data to support the durability of EV batteries, confidence in the technology is bound to grow. As more studies like Kvdbil’s emerge, the narrative around EV ownership is shifting — from “batteries wear out fast” to “batteries last longer than expected.”
Manufacturers like Kia, Tesla, Audi, and Volvo have long claimed that their battery packs are engineered for longevity, often backed by 8-year or 160,000 km warranties. Kvdbil’s findings provide independent validation of those claims, reinforcing that the technology has matured to a highly reliable standard.
What’s More?
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 after 1,45,000 kilometers. That’s already impressive. But keep in mind that battery degradation is most significant within the first couple of years. A car with around 2,10,000 kilometers on it still retained 85% of its original battery capacity. There are even plenty of examples of cars surpassing 3,20,000 or even 4,80,000 kilometers with 80% capacity or more.
Another key point is that most EVs sold today include an unusable “buffer zone” in their battery that’s hidden from the user. As the battery naturally degrades, this buffer gets activated to compensate for lost capacity. In practice, that means while the actual battery pack may lose some efficiency, the usable driving range often remains unchanged for the first 1,60,000 to 2,40,000 kilometers.
More good news: the RSEV charts likely represent a worst-case scenario, given the data set. RSEV is a used EV dealer in the U.K., and its analysis covers cars coming off lease. Leasing in the U.K. is common for company cars, typically lasting three to four years. So, not only have these vehicles covered 145,000 or 210,000 kilometers, but they’ve done so in a remarkably short time. Most privately owned cars would take close to a decade to reach that mileage, especially in India.
That means these EVs were driven hard, year-round, often relying on regular DC fast charging. They’re also primarily 2021 or 2022 models, and both battery pack technology and EV reliability have improved significantly since then.
The Road Ahead: Building Trust in Second-Hand EVs
The used EV market is still developing, and studies like this one from Sweden are key to building consumer trust. Buyers who might have hesitated due to fears of battery degradation can now approach the market with renewed confidence.
As Reinholdsson and his team have demonstrated, the combination of smart battery design, thermal management, and good user practices results in minimal capacity loss even after years of use.
The takeaway is clear: the myth of rapid EV battery degradation is officially busted.
With the evidence mounting, it’s becoming apparent that the batteries powering our electric cars today are not just durable — they’re redefining longevity in the automotive world.
