The longevity and performance of electric vehicle (EV) batteries have long been a subject of concern, especially for individual owners, businesses with fleet operations, and the burgeoning used EV market. A recent study conducted by TÜV NORD in collaboration with Carly in 2026 has shed light on a critical tipping point where EV battery degradation accelerates significantly. The findings not only challenge previous assumptions about battery durability but also offer actionable insights for fleet managers and consumers navigating the EV landscape.

Early findings and the tipping point

The study analyzed the battery health, or State of Health (SoH), of approximately 50,000 battery electric vehicles (BEVs) and plug-in hybrids manufactured between 2016 and 2026. SoH is an essential metric representing the remaining capacity of an EV battery compared to its brand-new state, with a score of 100 indicating no degradation.

The main takeaway is that, up to 90,000 kilometers (roughly 56,000 miles), EV batteries show minimal degradation, losing on average just 0.7 SoH points per 10,000 kilometers. Beyond this threshold, however, battery deterioration accelerates sharply, with an average loss of 2.3 SoH points for every additional 10,000 kilometers. This shift marks a crucial milestone—referred to as the 'tipping point'—where range, performance, and resale value start to decline noticeably.

Battery performance across mileage

The study revealed that most EV batteries retain excellent health in their early lifecycle. The median SoH rating across the examined sample stands at an impressive 96 points, reflecting only slight aging in the majority of cases. Vehicles with an SoH score between 90 and 100 exhibit negligible performance differences from new batteries, while those scoring between 85 and 90 show moderate wear but remain functionally adequate.

However, once an SoH drops below 85 points, the effects on range and charging efficiency become more pronounced. This drop has direct implications for both vehicle usability and market value. Notably, only 9.9% of the sampled vehicles fell below the 85-point threshold, dispelling fears that EV batteries degrade rapidly under typical usage scenarios.

Factors influencing battery degradation

The 90,000-kilometer tipping point highlights a correlation between mileage and battery wear, but the study stops short of clarifying whether vehicle age contributes equally to degradation. Additional factors such as charging habits, thermal management, and ambient temperature also play a role in battery health. For example, Geotab’s analysis indicates that frequent use of ultra-fast chargers can marginally accelerate battery degradation compared to regular AC charging, though still within acceptable limits.

Temperature extremes are another variable. Batteries tend to age faster in regions with consistently high temperatures, emphasizing the importance of robust thermal management systems. Individual driving behavior, while less impactful, can still influence degradation over time.

Brand-specific differences

The TÜV NORD and Carly report also shows notable variations in battery performance across different automakers. Older models from brands like Hyundai, Kia, and Mercedes-Benz demonstrate higher SoH values (90-95 points) compared to older Volkswagen, Renault, and Citroën models, which sometimes fell to the 70-80 range. Yet, this disparity diminishes in newer vehicles, with most models achieving SoH scores between 97 and 100 points. This suggests that advances in battery technology over the past decade have led to more durable systems across the industry.

Implications for fleet management

For businesses operating EV fleets, the identified tipping point carries significant operational and financial implications. Three key strategies stand out:

1. Battery health monitoring: Fleet managers are advised to regularly measure battery health, such as every 5,000 kilometers, to track degradation trends. For large fleets, it may suffice to sample SoH data from a few representative vehicles per make and model.

2. Range and service planning: Understanding when battery degradation accelerates allows operators to estimate the mileage at which a vehicle's range may no longer meet service requirements. This enables proactive vehicle replacements and ensures uninterrupted operations.

3. Maximizing resale value: Residual vehicle value depends heavily on battery health. Selling an EV before its SoH drops below 85 points can help fleets secure a better return on investment.

The used EV market and warranties

Battery health is perhaps the most critical factor for buyers in the used EV market, as it directly determines a vehicle's remaining useful life. Encouragingly, the study finds that modern EV batteries typically exceed the minimum performance thresholds guaranteed by manufacturers. Current warranties often promise a minimum residual capacity of 70% for eight years or up to 160,000 kilometers, yet most batteries perform significantly better.

For used EV buyers, checking the SoH of a vehicle is now a must. Models with delayed tipping points and higher SoH ratings offer longer reliability and reduced long-term ownership costs, making them more attractive options.

The road ahead

The findings from the TÜV NORD and Carly study paint an optimistic picture for the EV sector. The durability of modern EV batteries exceeds earlier expectations, especially in newer models benefitting from improved technology. However, the sharp acceleration in degradation past 90,000 kilometers serves as a reminder that maintenance, charging practices, and operating conditions remain crucial.

As fleets and individual owners continue transitioning to electric mobility, informed battery management will be key to maximizing value and utility. Whether you're planning to electrify a fleet or invest in a personal EV, understanding the dynamics of battery health—and the tipping point where degradation accelerates—will help ensure smarter decisions in the long run.