An EV battery health certificate can summarize state-of-health and diagnostic data collected during testing.
AVILOO has released a study examining electric vehicle (EV) battery degradation using data from more than 500,000 independent diagnostic tests conducted between 2022 and 2026.
The analysis covers 20 EV models and is based on the company’s FLASH battery diagnostic test, which connects through the vehicle’s OBD port and takes approximately three minutes.
Rather than relying solely on the state-of-health (SoH) value reported by the vehicle’s battery management system (BMS), the test uses a statistical model trained on data from comparable vehicles to calculate battery health.
The diagnostic process considers the vehicle’s internal battery-health assessment alongside operating and battery data, including mileage, age, charging cycles, cell-voltage spread, and energy counts. AVILOO’s broader diagnostic database contains more than one million battery tests from vehicles operating across multiple regions and climates.
For the study, AVILOO calculated the median battery SoH for each model at 50,000, 100,000, and 150,000 km. The analysis also includes a 99% prediction interval to show the variation among individual vehicles rather than relying only on an average value for each model.
The results show that median battery health generally declines as mileage increases, while the variation among individual vehicles tends to widen. Differences were also observed between examples of the same model, with SoH varying by as much as 13.5 percentage points.
Battery state of health and estimated range for four EV models at 50,000, 100,000, and 150,000 km. The bands show the central 99% distribution, with the median indicated by the black line. (Image: AVILOO)
Among four models examined in greater detail:
- Hyundai IONIQ 5, 72.6-kWh battery: Median SoH declined from 97.2% at 50,000 km to 92.8% at 150,000 km.
- Tesla Model Y, 78.8-kWh battery: Median SoH declined from 94.5 to 90.3% over the same mileage range.
- Volkswagen ID.4, 77-kWh battery: Median SoH declined from 95.3 to 90.6%.
- Nissan Leaf ZE1, 40-kWh battery: Median SoH declined from 91.1 to 86.3% and showed the widest variation among individual vehicles in the four-model comparison, reaching 13.5 percentage points at 150,000 km.
AVILOO’s data indicates that battery capacity and charging frequency can influence degradation. Smaller-capacity batteries require more charge and discharge cycles to cover the same distance, and the study found that smaller-battery EVs tended to show faster degradation.
The dataset includes vehicles from North and South America, Europe, Australia, and Asia, incorporating batteries operating under different temperature and driving conditions that can influence battery aging and charging performance.
“What matters is that battery health varies significantly between models, and even more between individual cars of the same model,” said Marcus Berger, CEO of AVILOO. “A gap of 10 or 15% in state of health is a real difference in range.”
AVILOO plans to publish the battery report twice annually.
Filed Under: Batteries, Technology News, Testing and Safety