Charging Cycle Life
Charging Cycle Life defines the number of complete charge-discharge sequences a storage system sustains before capacity degrades below a specified threshold (typically 80%). A cycle represents 100% throughput; partial cycles aggregate (e.g., two 50% discharges = one cycle). Distinct from Calendar Life, cycle life measures wear induced by active usage.
Determinants
- Depth of Discharge (DoD): Shallow cycling extends lifespan; high DoD accelerates degradation.
- state-of-charge (SoC): Prolonged high/low SoC induces structural stress on Electrode materials.
- Temperature: Heat accelerates Solid Electrolyte Interphase growth; cold increases internal resistance.
- Chemistry: LFP exhibits superior cycle stability vs. NMC; Solid-State electrolytes aim to eliminate dendrite formation.
- C-Rate: High current charging/discharging increases thermal load and mechanical strain.
Application Context: Electric Vehicles
- Insights from
[[lab-notes/2026-05-11-EV-Battery-Longevity-Actual-Degradation-Data-for-Buyers|EV Battery Longevity: Actual Degradation Data for Buyers]]:- EV battery longevity often misperceived by analogy to smartphone batteries; EV packs demonstrate significantly reduced degradation rates due to scalable Battery Management System (BMS) capabilities, active thermal management, and lower energy density constraints compared to portable electronics.
- While EVs utilize Lithium-Ion chemistry similar to consumer devices, the implementation differs drastically: EV cells operate within optimized voltage windows and benefit from cell balancing algorithms that prevent individual cell over-stress, yielding cycle lives frequently exceeding 1,000–2,000 full cycles.