Questions to ask about a used EV battery-health report

The short answer

A battery-health report is only useful if it clearly describes this specific car and you can understand what it measured. Before relying on one, ask six things. Who issued it? Which vehicle and battery does it cover? When was it done, and at what mileage? What method did it use? What exactly does each number mean? What did it leave out? If the seller or issuer cannot answer these in writing, treat the report as incomplete. Ask for a recent report or arrange a professional assessment of the car you are actually considering.

The most common confusion is between three different figures that can all appear as percentages or ranges on a report or dashboard:

State of charge: how full the battery is right now, like a fuel gauge. It says nothing about the battery's condition.
State of health (often shortened to SoH): an estimate of the battery's current capability compared with a reference point, usually its original capacity. How it is calculated depends on the method and the issuer.
Range estimate: a prediction of driving distance. It depends on charge level, recent driving, temperature and the car's own software, so it is not a direct measure of battery health.

A good report labels which of these it is showing. If it does not, ask the issuer to say so in writing.

Questions about where the report came from

Can I see the complete report, not a screenshot or summary page?
Who issued it? Was it the manufacturer, a dealer, an independent assessor or an app?
How can I contact the issuer directly? Find their contact details yourself rather than relying on details printed on the report.
Was the report produced for this sale, or for an earlier owner or a different purpose?

Contacting the issuer yourself lets you confirm the report is genuine and unaltered. It also lets you ask the follow-up questions below.

Questions about which car and battery it covers

Does the report show the vehicle identification number (VIN), and does it match the car and its title?
Which battery pack version or capacity does it refer to?
Has any battery work happened since the report was produced? This includes module or pack replacement, repairs or software updates.
If the battery was replaced or repaired, is there documentation for that work?

Later battery work can make an older report describe a battery that is no longer in the car. Without a VIN match, a report does not reliably describe this vehicle at all.

Questions about date and mileage

On what date was the assessment carried out?
What was the odometer reading at the time?
How far has the car been driven since then, and how much time has passed?

A report is a snapshot. The further the car's date and mileage have moved from the snapshot, the less the report tells you about the battery you would be buying. This is why buying guides commonly recommend asking for a recent report rather than accepting whatever document comes with the car.

Questions about method and scope

What method was used? For example, was it a reading taken from the car's own systems, or a measured test? Was it a quick check or a more extended assessment?
If software or a diagnostic tool was used, which version?
Is the method supported for this make, model and battery version?
What did the assessment cover, and what did it not cover?
What conditions applied during the test, such as charge level or temperature, if the issuer considers them relevant?

Scope matters as much as the headline number. A check that reads one stored value answers a narrower question than an assessment designed to measure capacity. Ask the issuer to explain in plain terms what their method can and cannot tell you.

Questions about the numbers themselves

What is the exact label for each figure? Is it state of health, usable capacity, gross capacity or estimated range?
What units are used? Is it a percentage or a capacity in kilowatt-hours (kWh)?
If it is a percentage, what is it a percentage of? Is the baseline the original rated capacity, a manufacturer reference or something else?
How much uncertainty does the issuer attach to the figure?
Are there any warnings, fault codes or notes elsewhere in the report?

Ask the assessor to walk you through these figures and their limitations before you compare them with anything else. A percentage without a stated baseline and method is hard to interpret, however reassuring it looks.

Comparing reports between cars

If you are weighing several used EVs, put each report's details side by side. A simple comparison layout looks like this:

Item	Car 1	Car 2
VIN on report matches car
Battery version or capacity
Issuer and independently found contact
Assessment date and mileage
Method and software version
Measurement label, value and units
Baseline the figure is compared against
Stated uncertainty
Exclusions and limitations
Battery work since the report
Questions still unanswered

Only compare figures that measure the same thing. Wait until each issuer has explained its definitions, baseline and method. Two reports showing the same percentage but using different methods may not be answering the same question. A higher number on one report does not automatically mean a better battery than a lower number on another. Where the manufacturer publishes documentation on how its vehicles report battery capacity or health, ask for it or check it for your model year.

There is no single passing percentage that applies to every EV. A battery-health figure also does not predict how many years or miles a battery has left. Use the report to understand the car's current condition as documented, not as a forecast.

Questions about warranty

How much of the manufacturer's battery warranty remains, by time and by mileage?
Does the warranty transfer to a new owner, and are there conditions or steps needed to transfer it?
How does the manufacturer define a covered capacity loss, and how is it measured for a claim?

Battery warranty terms vary by manufacturer, model year and market. Confirm them against the manufacturer's own warranty documents for the specific car rather than relying on general figures.

When there is no report, or you want your own: comparing assessment quotes

If the seller has no usable report, you can ask for a professional battery assessment before you commit. Prices and free offers vary by provider and location. Some dealers or programs advertise free checks. For any offer, free or paid, ask what is included and what written result you will receive.

Hypothetical example, not real prices: Assessment A is quoted at $160 plus $30 travel, for a total of $190. Assessment B is quoted at $220 including travel. B looks more expensive, but the totals alone do not settle it. Beside each total, note the following:

Does the provider support this make, model and battery version?
What does the assessment cover, and what does it exclude?
What written deliverable will you receive, and does it show the VIN, date, mileage, method, measurement labels, baseline and uncertainty?
Are taxes included?
Could any additional charges apply?

Choose based on which assessment answers your question for this car, with a report you can actually interpret. Price alone is not enough. Leave battery testing to a qualified assessor; high-voltage EV systems are not a do-it-yourself job.