Quick answer
SoH means state of health. A capacity-based battery SoH percentage compares current usable energy with a matching original reference: 54 kWh against 60 kWh is 90%. SoC, or state of charge, tells you how full the battery is now. A reported SoH needs its test method and baseline; it is not a remaining-life forecast.
Use the battery health estimator →SoH is a comparison, not the charge level
State of charge describes how full a battery is now. State of health describes its condition relative to a reference, but the method and definition matter. A capacity-based SoH result and a power-performance assessment need not describe exactly the same thing. Before comparing percentages, identify what each report measures and which new-battery baseline it uses.
A percentage needs a denominator
For a simple capacity comparison, 54 kWh divided by a 60 kWh original usable baseline equals 90%. If someone instead divides by a 65 kWh gross rating, the apparent percentage changes even though the battery has not. This is why the original baseline, measurement boundary and units belong alongside the result. An unnamed percentage in an advert leaves too much unexplained.
Reported BMS SoH remains reported information
The battery-management system uses vehicle data and its own estimation method. EVVerity can display a number you supply, but cannot authenticate the report or verify which car it belongs to. We label it “Reported BMS SoH” and keep it separate from the capacity inferred from range and consumption. Agreement between methods is useful context, not proof that either is exact.
What to ask when someone quotes SoH
Ask for the test date, odometer reading, method, reference capacity and any supporting service notes. Check whether the installed battery has changed since the report. Avoid translating a single percentage into a precise remaining lifespan. Your practical question is whether the documented condition, usable range and charging behaviour meet your needs, with uncertainties made explicit.
Three numbers that answer three different questions
A seller might show all three of the following values on one screen. They cannot replace one another. Read the name and reference before using any number in a calculator.
| Number | Meaning | What it does not establish |
|---|---|---|
| 80% state of charge | The displayed charge level now | That 80% of original capacity remains. |
| 90% capacity-based SoH | A condition estimate against a defined reference | Exactly how far the car will drive today. |
| 54 kWh usable capacity | Energy available under the stated method | The original gross pack rating or fault-free operation. |
Why “90% health” still needs explanation
Consider a hypothetical report with 54 kWh current usable energy and a 60 kWh usable reference. Its simple capacity ratio is 90%. At 18 kWh/100 km that energy implies 300 km before a reserve; at 24 kWh/100 km it implies 225 km. The same capacity ratio supports different range outcomes. A report can also use a reference or internal BMS definition that differs from this simple ratio. Ask the provider to state the method rather than converting an unexplained percentage into kWh yourself. A high confidence label on EVVerity concerns the evidence you supplied, not independent authentication of the report.
Before you rely on the answer
- What exactly is the reference capacity?
- Is the percentage reported by a BMS or derived from an energy test?
- What conditions and limitations accompany it?
Worksheets and numerical scenarios are original EVVerity editorial examples. They are not observed vehicle results or market-price data.
SoH vs SoC: a full battery can still have less capacity
State of charge (SoC) describes how full the available battery is now. State of health (SoH) compares an aspect of its condition with a reference. Charging to 100% SoC does not restore the original capacity or mean 100% SoH.
There is no universal percentage that makes every used EV suitable. A reported 90% needs a defined method and reference; then compare the resulting usable energy with your journeys, charging access and reserve. A capacity figure also does not rule out unrelated faults.
For an arithmetic example, a pack that originally offered 60 kWh and now offers 54 kWh has 10% less usable energy on that same basis. At 100% charge it has approximately 54 kWh available, not 60. This is a simplified capacity comparison; the vehicle’s reported SoH may use a different definition. Keep the original report alongside any calculation.
| Term | Question it answers | What to retain |
|---|---|---|
| State of health (SoH) | How does a defined battery characteristic compare with its reference? | Method, date and reference; capacity-based SoH is one approach |
| State of charge (SoC) | How full is the available battery now? | The charge percentage at the time of the observation |
| Usable capacity in kWh | How much energy is available on the stated basis? | Whether it is an original specification or a current assessment |
Put the explanation to work
Use your own vehicle information, check the assumptions and see the calculation.
Battery Health Estimator →EVVerity estimates are informational and are not a substitute for a professional battery diagnostic or pre-purchase vehicle inspection.
Sources & editorial basis
- Tesla — battery health: an example of a manufacturer diagnostic
- US Department of Energy — EV batteries
Source list reviewed 2026-09-23. Additional guidance carries its own review date. Practical checklists and worked examples are EVVerity editorial guidance. Read our methodology.
Related reading
- Interpret a reported SoH value
- Understand measured capacity loss
- Calculate a like-for-like capacity change
Apply this to a model
Check the model’s battery references, charging equipment and viewing checklist. Match the year and original market to the car you are considering.