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EV Evidence

Used EV evidence · UK

What battery State of Health means

Battery State of Health is a comparison against a stated reference, not a universal property with one agreed measurement. In the E2 Huo study, it means current calibrated usable capacity divided by initial calibrated capacity. Ask what was measured before using any SoH result in a UK used-EV decision.

IEEE Access: Bayesian Network Based State-of-Health Estimation for Battery on Electric Vehicle Application and its Validation Through Real-World Data

Reviewed

Key facts and evidence

For a UK used-EV decision, as of 13 August 2026, State of Health is only meaningful when the report names the metric and reference value. The E2 Huo study defines a usable-capacity ratio, while other methods can describe resistance instead. It does not establish pack safety, future range or a universal pass mark for an individual car.

IEEE Access: Bayesian Network Based State-of-Health Estimation for Battery on Electric Vehicle Application and its Validation Through Real-World Data

State of Health only becomes useful when its metric, reference value, vehicle identity, method and test conditions are stated.

Start with the denominator

The Huo paper uses a usable-capacity definition: calibrated current capacity is compared with calibrated initial capacity. A different tool may use a different reference or metric, so the label alone is incomplete.

Source and date

The definition comes from Huo and colleagues, published on 11 January 2021 and admitted to the E2 battery evidence build checked on 13 August 2026. The report-context rule comes from OZEV guidance verified by E3 on 12 August 2026.

What the label leaves open

SoH does not by itself identify the test temperature, stored faults, resistance behaviour, physical safety or future driving range. Those limits must remain visible rather than being folded into one reassuring percentage.

Next step

Before relying on SoH, request the vehicle-specific written evidence listed in E3 row e3-s11-008. If the issuer cannot state the metric and conditions, commission a fresh explanation or report from an EV-competent specialist.

What to do next

This definition does not assess roadworthiness or whether a particular vehicle should be driven.

Immediate action: Identify the metric and reference behind the reported SoH.

  • Do not rely on the result when its metric, reference, vehicle identity or test conditions are missing.

Checks that stay with this vehicle

  1. Request a written report that names the SoH metric, reference value, vehicle, date, method and test conditions.

    The report makes clear what the result compares and how it was obtained.

    Treat SoH as unverified if the percentage is unexplained or the report cannot be matched to the vehicle.

Professional hand-off

  • Use an independent EV-competent technician or manufacturer-authorised battery specialist if the report cannot be explained.

Questions this record can answer

What does the sourced evidence say about start with the denominator?

The Huo paper uses a usable-capacity definition: calibrated current capacity is compared with calibrated initial capacity. A different tool may use a different reference or metric, so the label alone is incomplete.

What does the sourced evidence say about source and date?

The definition comes from Huo and colleagues, published on 11 January 2021 and admitted to the E2 battery evidence build checked on 13 August 2026. The report-context rule comes from OZEV guidance verified by E3 on 12 August 2026.

What does the sourced evidence say about what the label leaves open?

SoH does not by itself identify the test temperature, stored faults, resistance behaviour, physical safety or future driving range. Those limits must remain visible rather than being folded into one reassuring percentage.

Sources