Cycle life
The number of full charge-discharge cycles a battery can deliver before its capacity falls to a defined end-of-life threshold, usually 70–80% of rated capacity.
Cycle life quantifies how many cycles a battery survives under specified test conditions: depth of discharge, C-rate, temperature and end-of-life criterion. Without these conditions the number is meaningless; a cell rated 6,000 cycles at 0.5C, 25 °C and 80% DoD may manage far fewer at 1C and 40 °C.
Example: 6,000 x 0.9 x 10 kWh x 0.9 ≈ 48.6 MWh
Typical cycle life to 80% capacity:
- Lead-acid (50% DoD): 500–1,500
- NMC: 1,000–2,500
- LFP: 4,000–8,000 or more
- Lithium titanate (LTO): 10,000–20,000
- Vanadium flow battery: more than 15,000, with electrolyte essentially indefinitely reusable
Batteries also suffer calendar ageing, which proceeds regardless of use and is accelerated by heat and high state of charge. A daily-cycled home battery doing 365 cycles a year reaches 6,000 cycles in about 16 years, so calendar life (often warranted at 10–15 years) usually binds first. Cycle life is a key input to LCOS.
Related terms
All terms →- Depth of discharge (DoD)
The fraction of a battery's capacity that has been discharged, or the maximum fraction a manufacturer allows to be used per cycle.
- C-rate
The charge or discharge current of a battery relative to its capacity; 1C empties a full battery in one hour, 0.5C in two hours.
- LFP (Lithium Iron Phosphate)
A lithium-ion cathode chemistry (LiFePO4) prized for safety, long cycle life and low cost, at the expense of lower energy density than nickel-based cells.
- NMC (Nickel Manganese Cobalt)
A family of lithium-ion cathodes (LiNixMnyCozO2) offering high energy density, widely used in long-range electric vehicles.
- LCOS (Levelized Cost of Storage)
The average cost per MWh discharged over a storage asset’s lifetime, including investment, operation, charging energy and efficiency losses.
- State of charge (SoC)
The remaining charge in a battery expressed as a percentage of its current full capacity.