Ayvens says almost 7,300 electric cars returned from leases in Germany retained average battery health of 95.5%, adding evidence to a question that affects buyers, dealers and leasing companies: how much useful battery capacity remains when an electric car changes hands?
The fleet-management and leasing company’s October 19 announcement puts average mileage at about 55,000 kilometers, or roughly 34,000 miles. Testing began in 2025 and took place before the cars were sold to private customers or used-car dealers.
The result describes Ayvens’ lease returns, not every electric vehicle on the road. It also provides a snapshot of remaining capacity, not a guarantee about future reliability or the number of years a battery will last.
For a buyer comparing two apparently similar cars, that snapshot can answer something the odometer cannot. Mileage records distance traveled. A battery report examines the condition of the expensive system storing the car’s energy.
Battery health is different from battery charge
State of health, commonly shortened to SoH, compares a battery’s condition with a reference for its condition when new. A capacity-based score of 95.5% indicates that most of the original capacity remains, subject to the testing method and reference used.
State of charge measures something else: how full the battery is at that moment. An older battery can be charged to 100% while holding less energy than it did when new. A full battery icon is not a battery-health certificate.
As an illustration, a battery with 60 kilowatt-hours of usable capacity when new would retain about 57.3 kilowatt-hours at 95.5% on the same capacity basis. A kilowatt-hour measures stored or consumed energy. The calculation is not a measurement of any car in the Ayvens sample.
Driving range cannot be read directly from that percentage. The US National Highway Traffic Safety Administration’s explanation of EV batteries describes how temperature affects performance and how thermal-management equipment itself consumes energy. A capacity test and a winter highway trip measure different things.
Ayvens says its used electric cars offered for sale carry an AVILOO battery-health certificate. AVILOO, which sells battery-testing services, separately reports an analysis of more than 500,000 tests and argues that similar mileage can conceal different battery conditions. Its commercial interest in diagnostics should be kept in view when assessing that argument.
Resale prices feed back into the cost of a new car
The International Energy Agency’s Global EV Outlook 2026 estimates that used electric-car sales exceeded 3 million in 2025 across China, five major European markets and the United States, about 35% above 2024. That total includes battery-electric cars and plug-in hybrids.
Resale values affect the first owner as well as the second. Leasing companies buy vehicles expecting to recover part of their cost when they sell them. The residual value is that expected value at the end of the lease. A lower expected resale price increases the depreciation the contract must cover, before financing and other charges.
Consider a deliberately simplified three-year example. A car costs €40,000. If it is expected to sell for €20,000 after 36 months, the depreciation allowance is €20,000, or about €556 a month. If the expected resale price is €15,000, that allowance rises to €25,000, or about €694 a month.
The difference is approximately €139 monthly. Those are our calculations, not quoted lease prices. Interest, taxes, fees, maintenance, timing and the lessor’s commercial terms would change an actual payment.
A credible battery record can reduce one uncertainty in that calculation. It cannot prevent a newer, cheaper model from reducing demand for an older one. The IEA describes how new-car price cuts, supply and technological improvements have affected used EV values.
What a buyer should ask a battery report to establish
The New York State Energy Research and Development Authority’s used-EV guide recommends checking vehicle condition, maintenance and accident history, range requirements and battery-warranty coverage. A battery report belongs alongside those records.
Before relying on a score, a buyer or fleet manager can ask:
- Does the report identify this vehicle, its mileage and the test date?
- What does the test measure, and what new-battery reference does the percentage use?
- Are there recorded faults, repairs or battery replacements that need explaining?
- What battery-warranty protection remains for the next owner, and what conditions or capacity thresholds apply?
- Can the car’s charging equipment and realistic range meet the intended daily work?
Those checks address different risks. A strong capacity score does not establish that the vehicle has never been damaged. A remaining warranty does not promise that every loss of capacity is covered. Buyers need the written terms for the particular vehicle.
Better records are also part of the wider battery market. As we reported in our coverage of EU battery passports, information about chemistry, condition and treatment can matter throughout a battery’s life. That policy framework should not be confused with a specific dealer’s diagnostic certificate.
The average is a starting point, not a valuation
Ayvens’ announcement does not provide the complete distribution of test results, a model-by-model breakdown or a controlled comparison with cars outside its fleet. Buyers cannot infer that a particular high-mileage car will score 95.5%, or that the same result applies to much older vehicles.
There is another limit to the evidence. The US National Institute of Standards and Technology’s 2025 battery-information research instrument sets out a proposed way to study how consumers value such information. It is a survey design, not a published finding that certificates raise every car’s selling price.
For dealers, the commercial task is to connect a dated test to the actual car and explain what the score covers. For fleet operators, it is to compare that evidence with resale proceeds and ownership costs. Neither can replace a vehicle-specific assessment with a reassuring fleet average.
