Cycle life is how many full charge/discharge cycles a battery can deliver before its capacity drops to a stated level (often 80%). It directly affects how long your solar battery bank will last. This guide explains cycle life and how to compare options.
What Is a Cycle?
One cycle = one full discharge (to the recommended depth of discharge) followed by a full recharge. In daily off-grid use, you might do about one cycle per day. So 3,000 cycles ≈ roughly 8 years of daily use; 6,000 cycles ≈ 16+ years (actual life also depends on temperature, rate, and DoD).
Cycle Life by Chemistry
- LiFePO4: Often 3,000–6,000+ cycles (to 80% capacity) at 80% DoD. Best choice for long-lived solar. See LiFePO4 vs lead-acid.
- Lead-acid (flooded, AGM, gel): Typically 300–1,200 cycles at 50% DoD. Fewer cycles and lower DoD mean shorter life and more replacements.
- Sodium-ion: Specs are still evolving; check datasheets. See LiFePO4 vs sodium-ion.
How to Compare
- Cycles to 80% (or similar): Higher is better. Note the DoD the manufacturer used (e.g. “3,000 cycles at 80% DoD”).
- Warranty: Many brands warranty years and/or cycles (e.g. “10 years or 6,000 cycles”). Compare warranty terms, not just cycle count.
- Real-world: Temperature, high DoD, and fast charging can reduce life. Conservative use (moderate DoD, not too hot/cold) helps reach the rated cycles.
Why It Matters for Solar
Off-grid solar cycles the battery every day. A 500-cycle lead-acid bank may need replacing in under two years; a 4,000-cycle LiFePO4 bank can last 10+ years. Even if LiFePO4 costs more upfront, total cost over time is often lower. Use the WattSizing calculator to size your bank; then compare cycle life and warranty when choosing a specific battery model.
