Before the viewing: ask for four records
Ask for the exact model year and battery version, a dated battery report if available, battery repair or replacement invoices, and the original warranty details. Request these before travelling. You can then check the model guide and identify what still needs an answer instead of spending the viewing searching for a battery-size number.
Keep an advert’s claims separate from the supporting records. “Long Range”, “new battery” and “still under warranty” each need clarification. A new battery might mean a replaced 12-volt battery rather than the traction pack. A registration date may describe an import rather than the model year. Write the exact unresolved question beside each claim.
Establish which battery the evidence describes
Match the report with the car and its current odometer. If a traction pack was replaced, check whether the report predates that replacement. Obtain the installed pack’s specification rather than assuming that a model name identifies it. Vehicle identifiers can be checked privately with the seller; you do not need to send them to EVVerity.
The calculator requires original usable capacity. A manufacturer’s gross rating includes energy outside the normal usable window. Dividing current usable energy by gross energy would count that buffer as degradation. If the source does not identify a usable figure, leave the health comparison unresolved and work with the documented range and charging evidence instead.
Understand the test before trusting its percentage
Ask whether the result is a battery-management-system estimate, a controlled capacity test or an inference from driving. These answer related questions using different evidence. Keep the provider’s method and limitations with the percentage.
Tesla’s Model 3 manual, for example, separates the Battery Health evaluation from an optional Battery Health Test. The test is not available on every vehicle, can require up to 24 hours on AC charging, and is recommended when there is concern about energy retention. That is a model-specific example, not a procedure to apply to every EV or improvise during a short viewing.
Worked example: a 90% report and a 320 km display
Suppose a seller provides a report stating 90% capacity retention against a documented 60 kWh usable baseline. That corresponds to 54 kWh if the report uses that capacity definition. Separately, a 320 km full-charge estimate paired with 16.5 kWh/100 km consumption implies 52.8 kWh, or 88% of the same baseline.
The two percentage points of difference are a question to investigate, not an automatic fault. First check that the consumption and range cover comparable conditions. A dashboard estimate based on a different driving history is not an independent capacity measurement. Do not average the two results or present the average as a better test.
| Record | Result | Next question |
|---|---|---|
| Capacity-based report | 54 kWh implied by 90% of 60 kWh | Which procedure and baseline did the provider use? |
| Range × consumption | 52.8 kWh, or 88% of the baseline | Do the two inputs describe the same conditions? |
| Difference | 1.2 kWh / 2 percentage points | Is a repeat measurement needed to resolve the uncertainty? |
At the car: check normal operation as well as range
Ask the seller to demonstrate ordinary AC charging and, where appropriate and safe, the DC system you expect to use. Note the starting charge, temperature, charger, elapsed time and any warning. A single peak-power photograph tells little about a complete charging session.
Check outstanding recalls through the manufacturer and the appropriate local authority before arranging demonstrations. NHTSA provides a US recall lookup; an imported vehicle may require checks in its original market as well. For physical damage, warnings or interrupted charging, use a qualified inspector. Do not open a high-voltage enclosure or attempt electrical measurements yourself.
Turn the evidence into a journey decision
With 54 kWh usable and an 80% departure charge plus 10% arrival reserve, the energy available for driving is 37.8 kWh. At an assumed 18 kWh/100 km, that supports 210 km. At 23 kWh/100 km, it supports about 164 km. Neither figure predicts your trip, but the comparison shows why a 180 km winter route deserves a charging plan even when the battery report looks reassuring.
Take away three separate conclusions: what is documented about the battery, whether the car charges normally, and whether the route works under demanding assumptions. If one remains unknown, list the specific document, demonstration or inspection needed. A health percentage is useful only when it helps answer those practical questions.
Which battery evidence do you have?
Choose the closest description for a useful next step. This does not diagnose the car.
I have a diagnostic report
Check the vehicle match, date, method and capacity reference. Enter any reported BMS SoH separately. If the report contains a different kind of derived health score, keep its original label and ask the provider how to interpret it.
Read the report checklist →The vehicle offers an onboard health test
Use the current owner’s manual for the exact vehicle. Confirm availability, preparation and duration with the seller. A test may not be practical during a short viewing; do not improvise a full discharge or change service settings.
Compare the test methods →I only have range and consumption
Use figures from matching conditions for an initial usable-energy estimate. Confirm the original usable baseline before calculating degradation. This does not measure SoH or establish whether a warranty claim qualifies.
Estimate with a visible sensitivity band →I do not have usable battery evidence yet
Age, mileage and VIN do not establish actual battery health. Request a recent report or discuss a suitable test with a qualified provider. Ask about supported vehicles, measurement method, scope and the final price.
See UK test-price examples and booking questions →Put the explanation to work
Use your own vehicle information, check the assumptions and see the calculation.
Battery Health Estimator →EVVerity estimates are informational and are not a substitute for a professional battery diagnostic or pre-purchase vehicle inspection.
Sources & editorial basis
- Tesla Model 3 manual — Battery Health and the optional test
- US Department of Energy — driving conditions and electric range
- NHTSA — US recall checks and the limits of search results
Source list reviewed 2026-10-26. Additional guidance carries its own review date. Practical checklists and worked examples are EVVerity editorial guidance. Read our methodology.
Related reading
Apply this to a model
Check the model’s battery references, charging equipment and viewing checklist. Match the year and original market to the car you are considering.