Estimate battery cycle life, service years, and lifetime delivered energy from rated cycles, depth of discharge, and daily use.
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Table of contents
How to use our Battery Cycle Life Calculator
- Enter Rated cycle life (cycles) and Rated depth of discharge (percent) from the battery data sheet or product listing.
- Enter Your regular depth of discharge (percent), which means the percent of the battery you expect to use before charging again.
- Enter Cycles per day and Battery size (kWh) so the calculator can estimate years of service and total delivered energy.
- Open Advanced options if you want to change Depth wear strength, Round-trip efficiency (percent), or End capacity for rating (percent).
- Sanity-check the result: if shallow cycling gives many more cycles but only a small gain in Estimated lifetime energy delivered, compare both values before choosing a use pattern.
Definitions
Rated cycle life: The number of charge and discharge cycles the manufacturer says the battery can complete under a stated test condition.
Depth of discharge (DoD): The percent of the battery's full capacity that is used before charging again; 80% DoD means 80% has been discharged [3].
Cycles per day: Your average number of charge and discharge cycles per day. One full daily use pattern is 1 cycle per day.
Battery size (kWh): The rated energy capacity of the battery pack in kilowatt-hours.
Round-trip efficiency: The percent of stored energy you get back after charging and discharging. It affects delivered energy, not the cycle count.
End capacity for rating: The remaining capacity at the end of the cycle-life rating period, often near 70% to 80% in battery cycle-life descriptions [2].
Equivalent full-battery cycles: Partial cycles converted to full-battery use. Two 50% cycles equal about one full-battery cycle.
Common mistakes and quick fixes
Mistake: Entering the battery warranty years in Rated cycle life (cycles) .
Fix: Use the cycle count from the data sheet, such as 3000 cycles, not the calendar warranty length.
Mistake: Leaving Rated depth of discharge (percent) at 100 when the rating was actually tested at 80%.
Fix: Match the manufacturer's rated DoD, because this is the reference point for the adjustment.
Mistake: Using remaining charge instead of used charge for Your regular depth of discharge (percent) .
Fix: If you use 60% of the battery and leave 40%, enter 60, not 40.
Mistake: Putting total days of use into Cycles per day .
Fix: Enter the average daily cycling rate, such as 1 for one cycle per day or 0.5 for one cycle every two days.
Mistake: Entering watt-hours in Battery size (kWh) without converting.
Fix: Divide watt-hours by 1000 first, so 10000 Wh becomes 10 kWh.
Mistake: Treating Estimated service life as a guaranteed battery age.
Fix: Use it as a cycle-aging estimate only; heat, storage charge, high current, and calendar aging can shorten real life.
Limitations & Key Assumptions / Boundary Conditions
- This is an estimate, not a warranty. Battery-specific cycle-life charts are better when available.
- The depth-of-discharge adjustment uses a simple power-law model. Real batteries can age differently by chemistry, cell design, temperature, charge rate, discharge rate, and state of charge.
- Estimated service life counts cycle aging only. Calendar aging can reduce capacity even when the battery is not cycled.
- Estimated lifetime energy delivered assumes capacity fades roughly evenly from 100% to the selected End capacity for rating (percent).
- Very high Your regular depth of discharge (percent), especially 100%, can be harder on many batteries than shallow cycling; the calculator still computes it because some data sheets rate full-depth use.
- The model uses the entered Round-trip efficiency (percent) as a constant. Real efficiency can change with power level, temperature, and battery age.
Methodology
Core cycle estimate
The calculator starts with the manufacturer's Rated cycle life (cycles) and adjusts it for the difference between Rated depth of discharge (percent) and Your regular depth of discharge (percent). Deeper discharge usually reduces total cycle count [2].
estimated_cycles = rated_cycles * (rated_dod_percent / planned_dod_percent) ^ depth_exponent
Depth wear strength sets the exponent: 1.0 for simple inverse, 1.3 for moderate extra wear, or 1.6 for strong extra wear. A larger exponent makes deep cycling reduce cycle life faster.
Service life and full-cycle comparison
The service-life estimate divides the adjusted cycle count by daily use, then converts days to years with 365.25 days per year.
service_life_years = estimated_cycles / cycles_per_day / 365.25
Equivalent full-battery cycles convert partial cycles to a common full-capacity scale.
equivalent_full_cycles = estimated_cycles * (planned_dod_percent / 100)
Lifetime delivered energy
The energy estimate uses battery size, planned DoD, round-trip efficiency, and average capacity over the battery's rating period. Average capacity is treated as a straight-line fade from 100% to the selected end capacity.
average_capacity_fraction = (1 + end_capacity_percent / 100) / 2
estimated_lifetime_energy_kwh = estimated_cycles * battery_capacity_kwh * (planned_dod_percent / 100) * (round_trip_efficiency_percent / 100) * average_capacity_fraction
The cycle change is kept signed, so a negative value means fewer cycles than the rating and a positive value means more cycles than the rating.
cycle_change_percent = (estimated_cycles / rated_cycles - 1) * 100
Mini-example
For a 10 kWh battery rated at 3000 cycles at 80% DoD, used at 80% DoD once per day, with 95% efficiency and 80% end capacity, the estimated cycle life stays 3000 cycles. Service life is 3000 / 1 / 365.25 = 8.21 years. Lifetime delivered energy is 3000 * 10 * 0.80 * 0.95 * 0.90 = 20520 kWh. Equivalent full-battery cycles are 3000 * 0.80 = 2400 full cycles.