BESS capacity fade
Loss of usable battery capacity as State of Health declines toward warranty limits.
Capacity fade is the gradual loss of a battery’s usable energy as its State of Health (SoH) declines. Warranties typically guarantee ≥70% SoH at 10 years; faster fade means the asset hits that floor early. Drivers are cycle count, temperature, high-SoC dwell, and depth of discharge.
Symptoms
- Measured usable capacity (kWh) trending below the warranty curve.
- A capacity test showing a step drop versus the previous test.
- Annualised degradation exceeding the contracted rate.
SCADA signatures
- SoH trend line projected to cross the 70% warranty threshold early.
- >5 percentage-point capacity drop between consecutive capacity tests.
- Degradation rate above 2× the contracted curve over a rolling 90-day window.
Root cause
Calendar ageing plus cycling. For NMC the dominant drivers are high average SoC and temperature; for LFP it is cycle count and temperature. Aggressive dispatch (deep daily cycles, high C-rate, hot operation) accelerates the fade.
Financial impact
Early capacity fade erodes the revenue capacity you can dispatch and can void or trigger the warranty. Detecting a 2×-contracted fade rate inside the 90-day window is the difference between a winning OEM claim and an out-of-pocket replacement.
How NuraVolt detects it
NuraVolt fits a linear SoH trend over a rolling window and extrapolates the days until the warranty threshold is crossed (an RUL "days-to-fault"), with the trend R² as the confidence. It cross-checks against the contracted degradation curve to raise a warranty-grade alert with the evidence attached.
Frequently asked questions
See also
Cumulative high-temperature exposure that accelerates battery degradation.
Falling round-trip efficiency as internal resistance rises.
Growing voltage spread between cells in a battery string.
The metric capacity fade is measured against.
Turning degradation evidence into a defensible claim.
See this on your own plants
NuraVolt turns your SCADA and BMS data into early fault detection, degradation-aware BESS analytics, and audit-ready reporting. A fixed-scope audit shows you what we’d find on your portfolio.