Capacity maintenance & the warranty fade threshold
Keeping usable capacity above the contracted curve over the asset’s life.
Capacity maintenance is the practice of keeping a BESS’s usable capacity above the curve its warranty and offtake guarantee — typically ≥70% State of Health at 10 years. The warranty fade threshold is the line that, once crossed, triggers a claim, an augmentation, or a penalty. Staying above it is the core long-horizon BESS management goal.
Definition
Every BESS warranty defines a capacity-retention curve (e.g. ≥70% at 10 years, ≥60% at 20) and a set of operating-window conditions that must hold for it to apply. Capacity maintenance is managing dispatch — depth of discharge, SoC window, C-rate, temperature — so the pack tracks at or above that curve, and detecting early when it is heading below.
Formula
Headroom = current SoH − contracted SoH(t) (must stay ≥ 0)
Typical range
Warranty floors: commonly ≥70% SoH at 10 years (or ≥60% at 20). A degradation rate sustained above ~2× the contracted curve over a 90-day window is the conventional warning that capacity maintenance is failing.
Why it matters
Whether the pack stays above its fade threshold decides three things at once: warranty standing, the timing of any augmentation spend, and offtake compliance. Catching a too-fast fade early can mean a warranty claim while you still have evidence; catching it late means an augmentation you pay for yourself.
How NuraVolt tracks it
NuraVolt continuously compares measured SoH to the contracted fade curve, raises a warranty-grade alert when degradation runs above the threshold rate, and links the cause (high-SoC dwell, C-rate, temperature) so dispatch can be corrected before the floor is breached.
Frequently asked questions
See also
The headline number for how much battery you have left.
Adding capacity mid-life to hold a contracted output as cells fade.
Turning operating data into a defensible — or contestable — warranty position.
How deep each cycle goes — and what it costs in lifetime.
The fault mode when capacity maintenance fails.
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.