How to Check Battery Health Before Buying a Used EV

Start by identifying what you are measuring

A useful battery check begins with the actual vehicle, pack and software configuration. Ask for the model year, exact variant, original market and any battery-replacement records. A registration year can differ from a model year, and a familiar badge does not establish usable capacity. Check that the baseline in your calculation belongs to the installed battery. Keep gross capacity, usable capacity and the current charge percentage in separate columns.

Collect evidence in a sensible order

Request a recent diagnostic report that identifies the vehicle, test date, method and mileage. Ask whether its SoH value is a BMS estimate or the result of an energy test. Manufacturer tools differ; Tesla, for example, documents a battery-health feature whose availability varies. Do not assume another model offers the same test. If the seller supplies only a dashboard range photo, treat that as context, not a capacity certificate.

Use range and consumption as a cross-check

An illustrative 320 km full-charge range at 16.5 kWh/100 km implies 52.8 kWh. The multiplication is exact; the inputs may not be. They must describe the same conditions and use battery-side consumption. Winter range combined with summer consumption can produce a misleading result. Repeat the estimate with a wider sensitivity band and compare it with the diagnostic evidence instead of forcing the two figures to match.

Finish with the questions numbers cannot answer

Ask whether the pack has been repaired, whether warnings have appeared, and whether both AC and DC charging work. Have a suitably qualified inspector assess the car, including visible underbody condition, charging equipment and documents. A capacity estimate cannot establish crash history, insulation integrity or the absence of an intermittent fault. If evidence conflicts, request clarification before drawing a conclusion. EVVerity helps organise the evidence; it does not certify the vehicle.

A viewing worksheet you can actually use

Keep an evidence sheet for each candidate. Record what you saw, when it was recorded and what remains unverified. Do not let a complete-looking spreadsheet hide missing evidence. The aim is to identify the next useful question, not to award a score.

Work through a conflicting example

Suppose the documents establish 60 kWh usable when new. A range of 320 km at 16.5 kWh/100 km implies 52.8 kWh, or 88% of that baseline. A seller also supplies a BMS report of 96%. Those figures differ by eight percentage points. Before interpreting the difference, check whether the consumption period matches the range estimate, whether the report belongs to the installed battery and whether winter conditions are involved. EVVerity flags the disagreement; it does not average the percentages. An independent diagnostic can answer questions the multiplication cannot.

Before you rely on the answer

• Does the report describe the battery installed today?
• Are the range and consumption from the same conditions?
• Which unresolved facts need the inspector’s attention?

Worksheets and numerical scenarios are original EVVerity editorial examples. They are not observed vehicle results or market-price data.