Battery SOH test: what does it tell you?
When buying a used electric car, the condition of the high-voltage battery matters. SOH (State of Health) helps assess it, but a single percentage cannot describe the entire vehicle.
What is battery SOH?
SOH describes the battery’s condition compared with a defined initial or reference condition. It is often expressed as a percentage. For example, a reading of 90% may suggest roughly 90% of reference capacity, depending on the measurement method and how the value is calculated.
SOH is different from SOC (State of Charge): SOC shows the current charge level, while SOH helps estimate long-term battery degradation.
Why check the battery before buying?
- More information about battery condition. Odometer mileage alone does not tell the whole story.
- Better context for the asking price. Consider SOH alongside vehicle history and other inspection results.
- Better questions for the seller. A report can highlight issues that merit further inspection.
- Documented information. Battery data can be useful when selling a vehicle.
How does an SOH test work?
Depending on the make, model and diagnostic system, SOH may be read from the Battery Management System (BMS) or estimated using a broader testing method. Some checks use an OBD diagnostic connection; others require a drive or additional data.
Not all electric vehicles and plug-in hybrids provide the same information. Confirm compatibility and what the selected test measures before booking.
Important: BMS-reported SOH, calculated capacity and real-world driving range may differ. A single SOH figure does not guarantee future range.
What else should you consider?
When available, look at battery chemistry, vehicle age and mileage, fault codes, temperature, cell-voltage data and limitations of the testing method.
Frequently asked questions
Does 100% SOH mean the battery is brand new?
No. The result depends on the manufacturer and calculation method and does not prove every battery component is fault-free.
Is SOH the same as driving range?
No. Range also depends on weather, speed, tyres, cabin heating and road conditions.
Can plug-in hybrid batteries be tested?
Some PHEV models provide suitable diagnostics, but compatibility must be checked for the specific vehicle.
Would you like to check your battery?
Compatibility and available diagnostic data depend on the model. Ask which tests and measurements are possible for your car.
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