Ownership tool
Battery health (SOH) estimator
Enter the original pack capacity and today's full-charge usable capacity — or derive it from one charging session — to estimate SOH, fade rate and where you stand against the 70% warranty line.
Battery state of health
90.7%
Good — within typical degradation
Battery state of health is about 90.7%.
| Current usable capacity | 68.0 kWh |
|---|---|
| Capacity lost | 7.0 kWh（9.3%） |
| Fade per year | — |
| Fade per 10k mi | — |
| Margin above 70% line | +15.5 kWh |
Context: US EV warranties typically cover the battery for 8 years/100k miles and most makers guarantee at least 70% capacity in that window — check your warranty booklet for the exact terms.
How it is calculated
SOH = current usable capacity ÷ original rated capacity × 100%. Enter a measured figure, or derive it: derived capacity = stall-side kWh × efficiency ÷ the SOC window charged.
Grades: SOH ≥90% is good, 80–90% normal wear, 70–80% worth an official test, below 70% under most makers' warranty line.
LFP packs outlast NMC on cycles but lose more usable capacity in the cold; 1.5–3% a year is typical for consumer cars, and heavy DC-fast-charge use or hot storage accelerates fade.
How to fill each field
- Current capacityPrefer a dealer test report or an OBD-read SOH. Otherwise read the stall's kWh for a session and use the derivation below — wider SOC windows are more accurate.
- Charge sessionStall readings include losses, so they are scaled by efficiency back to pack energy; a 10%→100% session gives the tightest estimate.
- Miles and ageOnly feed the fade-rate context — they do not change SOH itself. Leave 0 if unknown.
FAQ
How do I measure current capacity without test gear?
Derive it from one session: usable capacity ≈ kWh added at the stall × efficiency ÷ the SOC window. A 10%→90% session adding 55 kWh at 90% gives about 62 kWh. The derivation fields on this page do the math.
What SOH is normal?
Consumer EVs typically fade 1.5–3% a year, slightly faster in the first 20k miles. Above 90% at year three is good, 80–90% is the normal band; dipping under 80% within five years warrants a test.
What does the 70% warranty line mean?
US-market EV batteries carry at least an 8-year/100k-mile warranty, and most makers guarantee the pack stays above 70% capacity in that window — qualifying degradation is repaired or replaced. Terms vary by brand.
Do LFP and NMC packs fade differently?
Yes. LFP tolerates far more charge cycles and heat but loses more usable capacity in the cold; NMC holds more energy but ages faster if parked at 100%. Keeping daily use between 20–90% helps both chemistries.
How do I check battery health on a used EV?
Ask the seller for the range figure at a full charge, an OBD-reported SOH, or a dealer test report. You can also run one full session through this page for a rough figure before paying for an inspection.