Battery condition can vary by as much as 13.5 percentage points between used electric vehicles (EVs) of the same model and mileage, according to an analysis of more than 500,000 battery tests by diagnostics company Aviloo.
The Austrian company has published the first edition of its Certified EV Battery Report, covering tests conducted between 2022 and 2026 on 20 EV models in North and South America, Europe, Australia and Asia.
Aviloo calculated the median state of health (SoH) for each model at 50,000km, 100,000km and 150,000km. It also calculated a prediction interval intended to include 99% of tested vehicles at each mileage.
The results indicate that median capacity generally declines and variation between individual vehicles increases as mileage rises. Aviloo said the differences could materially affect the range and value of otherwise similar used EVs.
Among four examples highlighted in the report, the 72.6kWh Hyundai Ioniq 5 retained the highest median capacity. Its median SoH declined from 97.2% at 50,000km to 92.8% at 150,000km.
The 77kWh Volkswagen ID.4 declined from 95.3% to 90.6% over the same mileage range, while the 78.8kWh Tesla Model Y fell from 94.5% to 90.3%.
The 40kWh Nissan Leaf ZE1 recorded the lowest median figures of the four, declining from 91.1% at 50,000km to 86.3% at 150,000km. It also had the widest reported variation, reaching 13.5 percentage points at 150,000km.
Aviloo suggested that EVs with smaller batteries may degrade more quickly because they require more charging cycles to cover the same distance. However, the release did not disclose sample numbers for individual models or separate the results by vehicle age, battery version, climate or charging behaviour. Data for different battery sizes were combined under each vehicle model.
The analysis uses results from Aviloo’s three-minute Flash Test, which connects through the vehicle’s on-board diagnostics port. Its statistical model considers factors including mileage, age, charging cycles, cell-voltage variation and energy throughput alongside information supplied by the vehicle.
Marcus Berger, chief executive officer of Aviloo, said: “The truth in this data is that averages hide a lot. Yes, EV batteries are ageing better than the ‘they wear out fast’ myth suggests – but that’s not the most useful thing this report tells you.
“What matters is that battery health varies significantly between models, and even more between individual cars of the same model. A gap of ten or fifteen percent in state of health is a real difference in range, in what a car is worth, and in what you can rely on it for. You simply can’t know where your car sits in that range without testing it independently.”
Aviloo intends to publish the report twice yearly. Its complete diagnostics database now contains more than one million tests, although the present study uses a subset of approximately 500,000 results.
Photo: An Aviloo flash test is performed by connecting a device to the EV’s diagnostic port
