Introduction
Depth of Discharge (DoD) — the percentage of battery capacity used during a discharge — is one of the most influential factors affecting lithium-ion battery cycle life, performance and safety. Lower DoD generally results in significantly longer cycle life. This page explains the mechanisms, shows manufacturer data and provides practical recommendations for system design and operation.
Key Definitions
What is DoD?
DoD (%) = (Capacity discharged ÷ Rated capacity) × 100.
Example: If a 100Ah battery delivers 60Ah before recharge, DoD = 60%.
Why DoD matters
- Higher DoD → larger electrode strain per cycle → faster degradation.
- Higher DoD → more SEI growth → higher internal resistance.
- Combined with high temperature, high DoD accelerates capacity fade and safety risk.
Typical DoD vs. Cycle Life (summary)
Typical values (varies by chemistry, temperature, charge/discharge rates). These aggregated numbers are for illustration and planning.
| DoD (%) | Typical Cycle Life (approx.) | Estimated Service Years* (daily cycle) |
|---|---|---|
| 100 | ~500–800 | 1.5–2.5 |
| 80 | ~800–1500 | 2–4 |
| 50 | ~1500–3000 | 5–8 |
| 30 | ~3000–5000 | 8–12 |
| 10 | 6000+ | 16+ |
Manufacturer Data & Case Study (Huawen New Power)
Our LiFePO4 100Ah test bench:
| Test Condition | Result |
|---|---|
| 100% DoD | 80% capacity remaining after ~1,000 cycles |
| 50% DoD | 90% capacity remaining after ~3,000 cycles |
These results align with literature that reports a strong non-linear relationship between DoD and cycle life (see references below).
Interactive Charts
Cycle Life vs DoD
Estimated Years of Service vs DoD (1 cycle/day)
Capacity Retention Example — Huawen Test (LiFePO₄ 100Ah)
Practical Recommendations
- Keep daily DoD ≤ 80% for general applications; ≤50% when long lifespan is required.
- Configure BMS cutoffs (charge/discharge) to enforce DoD limits and protect cells.
- Design battery capacity with target DoD: increase buffer so users rarely hit full DoD.
- Control temperature: operate ideally between 15–30°C; avoid sustained high temps.
- Educate end users on charging habits — partial charges are fine and often better for long life.
Scientific Mechanisms & Notes
- Electrode mechanical fatigue: larger lithiation/delithiation swings cause micro-cracking.
- SEI growth & resistance rise: deeper cycling accelerates SEI reformation and thickening.
- Electrolyte breakdown: low-voltage and elevated temperature combined with deep cycles accelerate decomposition.
For detailed electrochemical explanations, see references [4,8,9] below.
References
- US Dept. of Energy — Battery Life Trade-Offs in Depth of Discharge, 2022.
- Battery University — BU-808: How to Prolong Lithium-based Batteries, 2023.
- IEC 62660-1 — Secondary Lithium-Ion Cells for Electric Road Vehicles, 2021.
- Ecker, M. et al., Journal of Power Sources, “Calendar and cycle life study of Li(NiMnCo)O₂-based 18650 batteries”, 2014.
- Huawen New Power — Internal test report (LiFePO₄ 100Ah), 2024.
Contact Huawen New Power
If you need custom battery packs, DoD optimization, or BMS configuration services, contact our engineering team for a tailored solution.
