Generational has published new analysis of around 10,000 used electric vehicle battery tests carried out through hundreds of automotive dealers across the UK, highlighting cell-level issues that can remain hidden by headline State of Health (SoH) figures.
The UK battery diagnostics company found that most used EV batteries remain well balanced. The median vehicle recorded a voltage difference of just 8 millivolts (mV) between its highest and lowest cells. However, around one in 85 tests identified a significant imbalance exceeding 50 mV, while approximately one in 200 showed an imbalance above 100 mV. Generational says the latter could indicate an underlying fault requiring further assessment.
Oliver Phillpott, CEO of Generational, said: “Reporting on State of Health is essential for used-EVs, but it does not tell the full story of battery condition. It measures capacity, not necessarily whether the cells inside the pack are functioning correctly.”
EV battery packs contain hundreds of individual cells which need to remain closely balanced. A cell drifting away from the others can cause the battery management system to restrict charging or discharging, potentially affecting range, charging behaviour and state-of-charge estimates. Generational’s cell-level diagnostics assess individual cells rather than relying solely on an overall battery capacity reading. The company said this can help identify vehicles operating normally while highlighting those showing signs of divergence.
Such problems may not produce warning lights or noticeable changes in vehicle behaviour, meaning faults can develop without the driver being aware. For dealers and finance businesses, unresolved issues can result in repair costs and lengthy cases involving customers.
Generational said battery testing is becoming increasingly important as more EVs enter the used market. SMMT data shows used battery electric vehicle transactions reached record levels during the first quarter of 2026. The company’s wider Battery Performance Index, based on more than 8,000 UK EV battery assessments, recorded average SoH of 95.15%. However, variation between vehicles increased with age, highlighting the importance of individual battery assessments.
The firm stated that verified battery data can help retailers price vehicles, protect residual values, reduce acquisition risks and give consumers greater confidence.
