🔋

Battery State of Charge & Cycle Aging

BESS Cycle Life · DoD · Calendar Aging

When to use: Estimating the service life of a battery energy storage system (BESS). Cycle life rises sharply at shallower Depth of Discharge — using cyclesAtDoD = baseLife × (100/DoD)^k. Heat accelerates degradation, roughly halving life per +10°C. Expected life is the lesser of cycle-limited and calendar-limited aging, to the typical 80% retained-capacity end-of-life.

Battery Parameters

Chemistry

Rated Capacity

kWh

Operating DoD5–100%

Cycles per Day

Avg Temperatureref 25°C

°C

End-of-Life Thresholdretained

Calculation Steps

Cycles@DoD = 4000 × (100/80)^0.8 = 4,782

Temp factor = 2^(−(25−25)/10) = 1.000×

Adj cycles = 4,782 × 1.000 = 4,782

Expected life = min(13.1 cyc-yr, 15.0 cal-yr) = 13.1 yr

Expected Service Life

13.1 yr

cycle-limited

Results

ChemistryLFP (LiFePO₄)

Cycles at Operating DoD4,782

Usable per Cycle80.0 kWh

Lifetime Throughput382.5 MWh

Cycle-Limited Life13.1 yr

Calendar-Limited Life15.0 yr

Expected Life13.1 yr

References

Cycle life rises at shallower DoD

LFP ~4000, NMC ~2000 cycles @100% DoD

Heat accelerates aging (~2× per +10°C)

EOL typically 80% retained capacity