Help CenterPerformance & Lifetime
Battery lifespan: cycles vs depth of discharge
How many cycles a battery can handle depends heavily on the depth of discharge it is cycled at. Discharging less deeply each cycle multiplies total lifespan — sometimes at the cost of a larger bank.
| DoD per cycle | LiFePO4 cycles (indicative) | Lead AGM/Gel cycles (indicative) |
|---|---|---|
| 100% | 2,000–3,000 | 150–250 |
| 80% | 3,000–6,000 | 300–500 |
| 50% | 5,000–8,000 | 600–1,000 |
| 20% | 8,000–15,000+ | 1,500–2,500 |
Two aging mechanisms overlap: cyclic aging (wear from charge/discharge cycles) and calendar aging (chemical degradation over time, even without use). A lightly-cycled but 10-year-old battery can be more degraded than a heavily-cycled but recent one.
Temperature strongly accelerates calendar aging: each 10°C rise above 25°C can roughly halve a lead-acid battery's calendar lifespan.
To compare two options economically, calculate the cost per kWh actually delivered over the lifespan: (Capacity × DoD × Cycles) gives cumulative kWh, divided by purchase price.
Common mistakes
- Comparing two batteries only on Ah capacity without accounting for recommended DoD
- Ignoring calendar aging for a lightly-used system (holiday home)
- Installing batteries in a poorly ventilated room where temperature regularly exceeds 35°C