Used EV battery health reports: how to interpret the results

First identify the assessment you are reading

Before comparing percentages, find out who issued the document and what procedure was used. A report may show a reading from the battery management system (BMS), a dedicated test, or both. These are not automatically equivalent measurements: the BMS calculates values using the manufacturer’s algorithms, while an independent assessment may use a different method and have a different scope. Ask what was actually measured, what data was used and what was left out. If the document does not explain this, treat the result as incomplete information, not a final verdict.

AVILOO distinguishes between a FLASH check and a more extensive PREMIUM assessment, and explains that the BMS’s SoH reading depends on the manufacturer’s algorithms. These are the provider’s descriptions, not a guarantee that a particular option is available or suitable for every car: confirm coverage, method and scope for the make, model and specific vehicle. Do not treat this explanation as an endorsement. We have not conducted these tests and do not claim an agreement with AVILOO.

Source: AVILOO · Métodos FLASH/PREMIUM y verificación de certificados ↗

Separate SoH, current charge and estimated range

State of charge indicates how much energy the car currently calculates is left; on its own, it does not measure how the battery has changed over time. State of health (SoH) is an estimate against some reference condition or capacity, but its precise meaning depends on the method and the definition of that reference. The range displayed on screen answers a different question: how far the system predicts the car may travel under the conditions it takes into account. These figures answer different questions and should not be substituted for one another.

A purely arithmetic example helps prevent a misleading comparison: 90% of a 60 kWh reference equals 54 kWh, while 90% of an 80 kWh reference equals 72 kWh. This does not establish that either capacity applies to a particular car. Likewise, multiplying an advertised range by an SoH percentage does not produce a real-world range test: it neither controls the conditions of use nor verifies how the percentage was obtained.

Check that the report belongs to this vehicle

Look for identification that links the document unambiguously to the vehicle being offered, as well as the assessment date and the mileage recorded at that time. Compare those details with the vehicle’s documents and the information in the listing; if they differ, ask for a documented explanation before relying on the result in a purchase decision. A partial image may omit exactly the fields needed to establish which car was assessed, so request the complete, legible report, not just its headline percentage.

Check the timeline too. A report describes what was examined on a particular date; it does not by itself confirm the present condition if repairs, component replacement or another relevant event occurred afterward. Ask whether battery-related work has been done and request any available records. Date and mileage cannot settle every technical question, but they help you judge whether the evidence is still relevant to the purchase you are considering.

Read the scope, conditions and anomalies

Find the method, test conditions, observations and any stated limitations. If an alert or anomaly appears, do not dismiss it as a footnote: ask what it means within that procedure, whether it affects the interpretation and what further check could clarify it. If the conditions are missing or the SoH reference is undefined, do not give the percentage more precision than the document supports. A decimal point cannot make up for a missing method or context.

Authenticity and technical interpretation are separate checks. AVILOO says a printed certificate can be checked against its digital original using a QR code; if you are dealing with that provider and the document offers this option, use it to check the original. Verification may help establish that a certificate is genuine, but it does not turn its findings into a commercial warranty or prove that the result answers every question you have. Separately confirm the vehicle identity and the scope of the assessment.

Source: AVILOO · Métodos FLASH/PREMIUM y verificación de certificados ↗

Relate the result to your regular journeys

Before deciding whether a result works for you, define what you need from the car: your usual journeys, whether you can charge where you park, and how much reserve you want for your trips. You do not need to turn those preferences into a universal SoH threshold. The same percentage may matter differently to buyers with different routines, and a report alone cannot predict the range you will get on every journey. Write down your requirements first, then use the evidence to see which questions remain unanswered.

As a hypothetical example, someone who mainly makes local trips and can charge at their usual parking place might value a different margin from someone who regularly drives longer distances with few charging alternatives. This does not prove that any particular battery is suitable for either buyer. It helps frame a useful question: what additional information would show whether this car meets my needs without relying on an optimistic estimate? If the answer requires data the report does not contain, request a specific explanation or further assessment.

Compare the report with the vehicle history

Consider the document alongside the maintenance history, declared repairs, messages or warnings observed, and an inspection whose competence and scope have been agreed. Ask who performed the assessment, which vehicle they examined and whether the technician could access information relevant to that model. Do not assume that a battery report covers the rest of the car, or that a general vehicle inspection necessarily answers every question about battery capacity or operation. Each document has its own scope.

A specific inconsistency is more useful than a vague concern. For example, if the mileage on the report does not match the mileage stated in the listing, ask for the figures to be reconciled; if an observation is unclear, request a written explanation and ask what test could resolve it. Do not assign a diagnosis to a warning without technical confirmation. Nor should the absence of a warning become a guarantee of future condition: the document reports on its assessment and date, not on how the vehicle will perform later.

Decide what is missing before reserving or paying

Summarize the case in four points: vehicle identity, report date and mileage, method and scope, and outstanding questions. If the details are consistent, keep the full document with the other records and evaluate the vehicle in light of your needs. If something does not add up, specify what evidence would resolve it: a verifiable original, an explanation from the issuer, records of a repair or a suitable additional assessment. An arbitrary discount is no substitute for that check; it may leave the uncertainty that matters to your decision untouched.

This guide sets no universal percentage that makes every battery good or bad, and promises nothing about range, service life, warranty or roadworthiness. Inspection, warranty and purchase terms depend on the individual case. Before reserving or paying, identify and verify who the seller is and who will receive the money; do not leave those checks until afterward. Keep the agreed terms in writing and confirm which document or inspection will be provided. The practical final step is to decide with enough evidence for your needs—or pause until the question that matters is answered.

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