They are two different measurements that happen to share the percent sign. State of charge (SoC) is how full the battery is right now, like a fuel gauge. State of health (SoH) is how much capacity the battery has left compared with when it was new, like the size of the tank. The big percentage on your dashboard is state of charge.
Key Takeaways
- State of charge is how full the battery is now; state of health is how much capacity remains versus new.
- The dashboard percentage is state of charge. State of health changes slowly, over years.
- Full charge plus reduced range in mild weather points to health; the same gap in winter is usually just cold.
- Watch SoC daily and SoH occasionally, especially before buying a used EV.
The Two Percentages Side by Side
| State of charge (SoC) | State of health (SoH) | |
|---|---|---|
| What it measures | Energy in the battery now, as a share of usable capacity | Usable capacity now, as a share of the original capacity |
| Where you see it | Dashboard and app, every day | Battery menu, app report or dealer report, if shown at all |
| How fast it changes | Every drive and every charge | Slowly, over months and years |
| What moves it | Driving and charging | Age, mileage, heat and charging history |
Confusion is easy because both are percentages, both live somewhere in the battery screens, and some cars do not display state of health at all. Our guide to how to check EV battery health covers the ways to find an SoH figure, from in-car data to a dealer report.
How the Two Numbers Interact
Range is where the two meet. The miles available are roughly the state of charge multiplied by the capacity the battery still has, which state of health describes. A car charged to 100% SoC with an SoH in the low nineties holds fewer kWh than it did when new, so its full-charge range is shorter. Nothing is broken; the gauge reads full, but the tank is slightly smaller.
Short-term changes are different. Cold weather cuts the range shown at any state of charge, and the miles come back when the battery warms up. That is a temporary effect on usable energy, not a change in health. As our look at whether EV batteries degrade over time explains, real capacity loss is slow: FuelEconomy.gov notes batteries may last 12 to 15 years in moderate climates and 8 to 12 years in severe ones.
Which One Should You Watch?
Day to day, watch state of charge: it tells you whether you can make the trip. State of health matters at longer intervals, and most of all when buying a used EV, where it is the closest thing to an odometer for the battery. Checking it once or twice a year, under similar conditions, is enough to spot a trend.
Charger data can help at home. A charger that displays energy delivered, such as the EVDANCE EV-ACS4005T 40A NACS portable charger, lets you note the kWh added between two known charge levels and compare like with like over time. A sudden drop, or warning lights, is a reason to have the car checked by a dealer rather than a puzzle to solve from the dashboard.
Frequently Asked Questions
Can state of health go back up?
Not in any lasting way. Readings can wobble slightly with temperature and with how the car measures, but lost capacity does not return. A small gradual decline over years is normal.
My car shows 100% but less range than when it was new. Is that SoC or SoH?
The 100% is state of charge: the battery is as full as it can currently get. The missing range reflects state of health if the gap persists in mild weather, or simply cold conditions if it disappears in spring.
Does charging to 100% damage state of health?
Holding any battery at extremes is harder on it than the middle range, and your car’s manual gives the maker’s guidance for daily use. Occasional full charges for long trips are a normal part of ownership; see whether Level 2 charging shortens battery life for the longer discussion.
Related Reading
- How to Check EV Battery Health
- Does an EV Battery Degrade Over Time?
- How Many kWh Does It Take to Charge an EV?
- Can an EV Battery Be Replaced or Repaired?
