Feature · 3 min read
Battery State of Charge & State of Health Explained
How full the battery is today, versus how much capacity it has left as it ages.
What's the difference?
State of Charge (SoC) is how full the battery is right now — the percentage shown on the dashboard. State of Health (SoH) is how much of the original usable capacity the battery still holds after years of use, expressed as a percentage of when it was new.
How does it work?
The car's battery management system continuously tracks voltage, current and temperature across the cells. SoC is recalculated constantly as you drive and charge. SoH is estimated over much longer periods — months and years — by comparing actual capacity to the original specification.
What does it feel like?
SoC is obvious: 80% means roughly 80% of usable range. SoH is invisible day to day but very relevant to a second-hand buyer. A three-year-old EV with 92% SoH has lost about 8% of its original range — at 100% on the dashboard you now get a little less mileage than the brochure promised when new.
Why it matters
- ✓SoH affects resale value of a used EV
- ✓Most manufacturer battery warranties cover SoH down to about 70%
- ✓Helps explain why range estimates drop slightly over the years
- ✓Useful when comparing two second-hand cars with the same mileage
Limitations
SoH is an estimate, not a precise measurement, and different brands calculate it differently. Some cars expose it in the menus; others only show it via a dealer diagnostic tool or a third-party reader.
Common problems
- ✓Inaccurate SoC reading after a long period unplugged
- ✓SoH not shown in the dashboard menus
- ✓Confusion between dashboard percentage and 'true' battery percentage including the protected buffer
- ✓Sudden drops in displayed SoH after a software update recalibrates