Linear Battery Aging Calculator

• C0_Ah
• N_cycles
• years
• k_cycle
• k_cal

• capacity_Ah
• SOH
• fade_frac

• Independent linear cycle + calendar fade
• Default k_cycle=0.0002/cycle and k_cal=0.02/year are illustrative
• N should match the cycle definition used to calibrate k_cycle; EFC recommended
• Not temperature, SOC, DoD, C-rate, or chemistry aware

• Ah, cycles, years

• C0≤0 → VALUE_MUST_BE_POSITIVE
• N, years, k_cycle, k_cal < 0 → VALUE_MUST_BE_NON_NEGATIVE
• Unclamped fade > 1 → SOH=0 and C=0

9 published on this page · 14/14 tests · Production surface contract 4/4 · View evidence

• C0=3 N=500 years=1 (defaults) → C=2.64, SOH=0.88
• C0=3 N=0 years=0 → C=3, SOH=1
• C0=3 N=500 years=1 k_cycle=0.0001 k_cal=0.01 → C=2.82, SOH=0.94
• C0=3 N=10000 years=0 → C=0, SOH=0
• C0=0 → error VALUE_MUST_BE_POSITIVE
• N_cycles=-1 → error VALUE_MUST_BE_NON_NEGATIVE
• years=-1 → error VALUE_MUST_BE_NON_NEGATIVE
• k_cycle=-0.001 → error VALUE_MUST_BE_NON_NEGATIVE
• k_cal=-0.01 → error VALUE_MUST_BE_NON_NEGATIVE

• Smith, K.; Neubauer, J.; Wood, E.; Jun, M.; Pesaran, A. — Models for Battery Reliability and Lifetime: Applications in Design and Health Management — NREL/PR-5400-58550 · 2013 · accessed 2026-09-05
  Supports: Institutional evidence that battery lifetime models combine cycle and calendar degradation, with coefficients that depend on temperature, DOD, voltage/SOC, and other stress factors — not a single universal linear law. CalculatorX uses a deliberately simplified linear approximation, not the NREL life model. (Distinct from NREL/CP-5400-57746, which has a different author list.)
• Saldaña, G.; San Martín, J. I.; Zamora, I.; Asensio, F. J.; Oñederra, O.; González-Pérez, M. — Empirical calendar ageing model for electric vehicles and energy storage systems batteries — Calendar fade vs storage time, temperature, and SOC · 2022 · DOI · accessed 2026-09-05
  Supports: Shows calendar ageing is commonly modeled with a power of time (often near t^1/2) and is strongly sensitive to storage temperature and SOC. Documents why CalculatorX linear-in-years k_cal is an illustrative first-order stand-in, not the complete empirical model.
• NREL — Battery lifespan modeling (BLAST / life-model overview) — Calendar and cycle aging, operating windows, and stress factors · accessed 2026-09-05
  Supports: Public institutional overview that lifetime prediction must consider temperature, operating windows, charge/discharge rates, storage environment, and cycling patterns. Used here to bound the scope of the linear model — not as a coefficient source.

• Linear approximation, not a digital twin — CalculatorX uses a deliberately simplified independent linear cycle + calendar model. It is not the NREL BLAST/life model, not an Arrhenius / √t calendar fit, and not chemistry-specific.
• Illustrative default coefficients — If k_cycle or k_cal is omitted, the engine uses 0.0002 /cycle and 0.02 /year. Explicitly supplied coefficients keep user-specified provenance even when the numeric values match those defaults.
• Cycle count / EFC semantics — N_cycles is a dimensionless cycle count matching the calibration of k_cycle — the engine does not assert that a caller’s N is EFC. Prefer EFC from discharged-Ah throughput ÷ C_nom when applicable. If charge+discharge throughput is accumulated, use EFC = (Ah_charge + Ah_discharge)/(2·C_nom) consistently — do not mix conventions.
• Schema pin follows calculation_version — Published input/output schema pins are keyed by calculation_version. Contract-only tightenings (normalized inputs, required result fields, required input_provenance) bump the patch version even when the fade formulas are unchanged, so latest alias and /{version}/ pins stay body-identical except $id. A future api_contract_version pin may decouple this further.
• Capacity clamp and fade_frac — SOH = max(0, 1 − k_cycle·N − k_cal·t). fade_frac is the unclamped linear exposure k_cycle·N + k_cal·t and may exceed 1; remaining capacity and SOH are clamped at 0. Actual capacity loss fraction is 1 − SOH. fade_frac is a required formal output.