Used ev battery health: the 90,000km threshold you need to know
Thinking of buying a used electric vehicle? Don't just check the mileage. There's a critical number – 90,000 kilometers – that can make or break your investment, according to a new study. Ignoring it could mean a significant drop in range and resale value.
The hidden degradation curve
A joint study by TÜV Nord and Carly, analyzing a robust sample of 50,000 vehicles, reveals a surprising truth about EV battery health. While the industry has long maintained gradual degradation is the norm, the data paints a different picture. For the first 90,000 kilometers, battery degradation is minimal, often barely noticeable in day-to-day driving. But beyond that mark, the rate of decline accelerates—more than threefold, to be precise.
TÜV Nord, a respected German technical inspection organization with a reputation mirroring decades of rigorous scientific testing, collaborated with Carly, a vehicle diagnostics specialist, to conduct this in-depth analysis. The data encompasses electric and plug-in hybrid vehicles manufactured between 2016 and 2026, providing a broad perspective on battery longevity across various models.
The key metric is State of Health (SoH), a percentage representing the battery's remaining capacity compared to its original state (100% SoH). A SoH above 90 indicates excellent condition; 85-90 suggests moderate but acceptable wear; and below 85, range and charging performance begin to suffer, directly impacting the vehicle’s value.
Most evs still hold strong
Contrary to common anxieties about rapid battery decay, the study’s findings are reassuring. A remarkable 96% of the vehicles analyzed exhibited a SoH above 85, meaning their batteries retain nearly all of their original capacity. Just 9.9% showed a SoH below this critical threshold. Notably, models produced from 2022 onwards consistently demonstrate SoH values between 97 and 100, highlighting significant advancements in battery Technology over the past five years.
The average degradation rate is a mere 0.7 SoH points per 10,000 kilometers driven—a gradual decline virtually imperceptible in typical use—until that 90,000km inflection point. Afterward, that rate jumps to 2.3 points per 10,000km. Consider this: a vehicle with 120,000 kilometers on the odometer might present an SoH of 85-88, representing a 12-15% range reduction from its original performance. That difference will be keenly felt on long journeys or in extreme temperatures.
Not all brands age equally
The study also uncovered significant brand-specific variations. Hyundai, Kia, and Mercedes-Benz consistently outperformed others, maintaining SoH values above 90 even in older models. This reflects superior thermal management systems and durable cell designs. Volkswagen, Renault, and Citroën displayed lower SoH values within the same age range, with some brands showing up to 10-point differences. However, the latest models from all manufacturers are converging, demonstrating a sector-wide maturation process.
While uncertainty surrounding battery health has long been a barrier to entry for the used EV market, the TÜV Nord and Carly data provides a much-needed benchmark. The vast majority of batteries are in good shape, manufacturers have made substantial improvements, and prospective buyers now have a crucial data point—the SoH—to guide their decisions. Don't buy a used EV based on mileage alone; demand the SoH report. It’s the single most important factor.