State of health and capacity fade
What SOH means, how it is measured, and what warranties promise.
You'll learn
- Explain state of health and capacity fade at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real pack
Overview
State of health compresses two different ageing effects — lost capacity and risen resistance — into one percentage. Know which one your number refers to.
In depth
Degradation simulator
Model calendar and cycle ageing under your own habits.
Years of ownership8 yr
Annual mileage15,000 km
Pack capacity75 kWh
Rapid charging share20 %
Average climate20 °C
Time parked above 90% SOC30 %
Estimated SOH
91.4%
Capacity remaining
68.5 kWh
Capacity lost
6.5 kWh
Range lost (at 18 kWh/100 km)
36 km
State of health over time
0 yr8 yr
Stays above the 80% warranty threshold for the whole period modelled.
| Metric | Meaning | Effect on the driver |
|---|---|---|
| Capacity SOH | Remaining usable kWh vs new | Lost range |
| Power SOH | Resistance rise vs new | Slower charging, weaker acceleration |
| Warranty threshold | Usually 70% capacity at 8 years / 160,000 km | Free repair or replacement below it |
Key takeaways
Remember this
- SOH covers capacity fade and resistance rise.
- The first few percent are lost quickly, then ageing slows.
- Warranties typically guarantee 70% at eight years.
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