Start with the report’s identity, date and scope
Before reading the large percentage, find the vehicle details, mileage, test date and provider. Compare these with the car being sold. Ask about pack replacements or relevant repairs after the test. A well-presented document for an earlier battery does not describe the installed one.
Next, read what was actually assessed. A report may describe energy retention without covering underbody damage, charging hardware or every electrical fault. A missing inspection item is not a passed inspection. Record the scope before deciding what further checks to arrange.
Find the method behind “SoH”
A BMS result is an estimate supplied by the vehicle’s battery-management system. A capacity test follows a procedure to assess available energy. A calculation from driving range and consumption is a separate inference. The report should make its method understandable, including any relevant conditions and limitations.
Tesla’s manual illustrates why names matter: its Battery Health evaluation and optional Battery Health Test are distinct features. Do not assume that a screenshot with the word “health” is the longer test. For any provider, ask which procedure produced the result and what it can establish.
A denominator error can change the conclusion
Consider an illustrative report showing 54 kWh against a 60 kWh original usable baseline. Capacity retention is 54 ÷ 60 = 90%. If the same 54 kWh is divided by a 65 kWh gross rating, it becomes about 83.1%. The apparent seven-percentage-point difference comes from the reference, not a change in the battery.
Check the original capacity definition, exact battery version and whether a software or hardware change affects the comparison. A report that does not state its baseline leaves an important part of the calculation unexplained.
| Field | What to establish |
|---|---|
| Capacity reference | Usable or gross; original pack or replacement pack |
| Method | BMS estimate, measured energy or another defined procedure |
| Date and mileage | Whether the evidence still describes this car |
| Conditions and coverage | Temperature, charge window and items actually inspected |
| Conclusion | Capacity only, or a wider assessment with supporting observations |
Do not turn a charging receipt into a capacity certificate
If a charger delivers 40 kWh while the dashboard moves from 20% to 80%, dividing 40 by 0.60 gives 66.7 kWh. That shortcut treats every billed kWh as energy stored and assumes the indicated percentage window precisely maps to usable energy. Those assumptions are not established by the receipt.
Under a chosen 10% loss scenario, only 36 kWh would reach the battery, giving 60 kWh for the same simple calculation. This example explains the measurement boundary; it is not a recommended DIY capacity test. Use the testing provider’s documented procedure rather than trying to create a definitive report from a single public charge.
When two reports disagree, preserve both explanations
Suppose a newer report shows 91% and an older one 88%. That does not automatically demonstrate that the battery recovered three percentage points. Check whether the provider, method, denominator, pack or conditions changed. Ask the provider to explain the comparison instead of selecting the more attractive number.
Likewise, a small change between comparable reports does not establish a constant yearly loss rate. Keep the dated records and seek interpretation of material unexplained changes, particularly if they coincide with warnings or charging problems. Do not diagnose an individual cell from a voltage number without the relevant procedure and limits.
Use a short follow-up request
Ask the seller or test provider to confirm the exact vehicle and installed pack, the method used, the original usable-capacity reference, any conditions affecting the result, and which inspection items were outside the test. Request the complete report rather than a cropped percentage.
Enter a reported BMS figure in EVVerity’s separate BMS field only when the document identifies it that way. A value from another test remains a result from that test. You can use documented current usable capacity in the range calculator, but a transcribed number does not become independently verified simply because a calculator displays it.
Put the explanation to work
Use your own vehicle information, check the assumptions and see the calculation.
Used EV Analyzer →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 — batteries for electric vehicles
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
- EV Battery Health Tests: Methods, Reports and Limitations
- EV Battery Health Test Cost in the UK: Dated Price Examples
- EV Battery SoH Meaning: State of Health Explained
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.