This popular EV battery was the clear loser in a major degradation study

A large-scale battery-degradation study drawing on nearly 10,000 electric-vehicle battery tests has put some of the most popular EVs on the clock — and the results are not evenly distributed. While the Kia e-Niro and Hyundai Kona Electric retained more than 97% of their original battery capacity after 62,000 miles, one Tesla Model 3 battery configuration averaged just 88.2%. That gap raises important questions for used-EV buyers, especially because two outwardly identical versions of the same model can age very differently.

The analysis comes from Swedish used-EV marketplace Carla, which examined 9,954 battery tests conducted between 2022 and 2026 using AVILOO battery diagnostics. It included models from Tesla, Audi, BMW, Kia, Hyundai, and several other manufacturers. More importantly, the results show that battery chemistry and supplier can matter as much as the badge on the car—a distinction used-EV listings rarely make obvious.

What 97% Retention Actually Means — And Why The Gap Matters7

The Kia e-Niro equipped with a 64-kWh battery led the model rankings, retaining an average of 97.25 percent of its original battery capacity after more than 62,000 miles. The closely related Hyundai Kona Electric finished just behind it at 97.18 percent, while the 77.4-kWh Kia EV6 placed third at 95.95 percent. For a vehicle originally capable of traveling 300 miles on a charge, 97 percent retention would theoretically represent a loss of only about nine miles, although real-world range also depends on temperature, driving conditions, and efficiency.

The practical math becomes more noticeable at 88.2 percent retention, the lowest figure disclosed in the study’s Tesla Model 3 battery breakdown. Applied to a hypothetical 300-mile starting range, that percentage would leave approximately 265 miles—a theoretical reduction of about 35 miles. That could affect charging behavior on road trips and leave drivers with less flexibility in cold weather, although capacity loss does not always translate perfectly into an equivalent reduction in displayed or real-world range.

The Study's Bottom Performer: A Buyer-Warning Flag

The weakest disclosed result belonged to the Tesla Model 3 equipped with a 52.4-kWh Panasonic battery pack. After more than 62,000 miles, that configuration retained an average of 88.2 percent of its original capacity. The larger 77.8-kWh Panasonic-equipped Model 3 performed only slightly better at 89.8 percent. Importantly, this was the lowest battery-health figure disclosed in the published breakdown, not proof that the Model 3 was the worst-performing vehicle across all 9,954 tests.

What makes that result especially relevant is how differently other versions of the same car performed. Model 3s using LG Chem batteries retained 91.5 percent, while those equipped with CATL-supplied lithium iron phosphate batteries averaged 93.3 percent. The gap between the strongest and weakest Model 3 configurations was therefore 5.1 percentage points—even though they all share the same model name.

That does not mean every Panasonic-equipped Model 3 will have exactly 88.2 percent capacity at 62,000 miles. Battery health varies with age, climate, charging habits, software, and usage. However, the study demonstrates why used-EV buyers should investigate the battery fitted to a particular vehicle rather than relying solely on the model badge.

Before buying a used Model 3, shoppers should request a battery state-of-health report and confirm the pack type when possible. Tesla battery information may be available through the vehicle’s documentation, service menus, diagnostic tools, or manufacturing details, but buyers should avoid assuming that every Model 3 from the same year uses the same cells.

Resale Value Follows Battery Health

Battery degradation and resale value are closely connected because remaining capacity affects how much usable range the next owner receives. A Model 3 retaining 93.3% of its original capacity should present a stronger ownership proposition than an otherwise comparable example sitting at 88.2%, provided mileage, condition, equipment, and price are similar. The problem is that conventional used-car listings rarely identify battery health or cell supplier as clearly as they identify trim and mileage. For reference, the base Model 3 RWD utilizes the CATL LFP pack, while the Long Range AWD and Performance models utilize the Panasonic packs; the Long Range RWD trim uses the LG Chem pack.

The study could therefore make battery documentation increasingly important in used-EV negotiations. A seller who can demonstrate strong battery health has evidence supporting the asking price, while a buyer considering a more heavily degraded example has grounds to negotiate. The 5.1-point spread among Model 3 battery configurations illustrates why two apparently similar cars should not automatically be valued the same way.

What Buyers Should Take Away From This Study

The headline takeaway is not that the Tesla Model 3 universally suffers from excessive degradation. It is that battery supplier and chemistry can produce meaningfully different results within the same model. In Carla’s data, the CATL LFP-equipped Model 3 retained 93.3% capacity after more than 62,000 miles, compared with 88.2% for the version using the 52.4-kWh Panasonic pack.

The broader model ranking was encouraging. The Kia e-Niro and Hyundai Kona Electric both retained more than 97%, and every vehicle in the published top 20 remained above 91%. Nevertheless, the Model 3 battery breakdown gives used-car buyers a concrete reason to look beyond mileage and model year. A lower purchase price may not represent better value if the car also has less usable battery capacity and range remaining.

Additionally, this study serves as a sort of reassurance to buyers considering going electric. It would take years for the average driver to reach the mileage used in the study, with U.S. drivers averaging approximately 14,000 miles per year. And even after that threshold is crossed, owners can trust the battery has retained a majority of its capacity. For new car buyers, this means years of worry-free ownership. For those shopping the used market, it means confidence and bargaining power. Battery studies of this scale remain relatively uncommon, and these results offer buyers a useful additional comparison point. Buyers who take the time to look up where a specific model lands in the degradation rankings before signing paperwork are in a meaningfully better position than those who don't.

Source: Carla