Battery cycle life calculator

Turn a cycle cap into years at your daily use, then count one day of readings under four rules and see how each changes the years.

Read this first. Every default is an invented placeholder, not a product's data or a real warranty. A warranty may count cycles in its own way, which these rules may not match: read its definition. Use a dot for decimals; "10,000" is read as ten thousand. Separate readings with spaces or new lines. No capacity fade is modelled.

1. Cycle cap to years

Capacity the cycle rule uses (kWh) Energy out per day (kWh) Cycle cap (cycles) Warranty term (years)

Result	Value
Cycles per day (kWh out ÷ capacity)	-
Cycles per year	-
Years until the cap is reached	-
Which comes first	-
Cycles used by the end of the term	-
Cycles per day at which the cap and the term meet	-

2. Count one repeating day from state-of-charge readings

State-of-charge readings (% of the capacity below), in time order. The last must equal the first.

Capacity the readings refer to (kWh) Capacity the cycle rule uses (kWh) Cycle cap (cycles) Warranty term (years)

Result	Value
Energy out in the day	-
Equivalent full cycles (energy out ÷ rule capacity)	-
Separate discharge periods	-
Rainflow cycles (depth as % of the readings' capacity)	-
Years to the cap: equivalent full cycles	-
Years to the cap: one cycle per day	-
Years to the cap: rainflow cycles counted whole	-
Years to the cap: each discharge period	-

A discharge period is a run of falling readings; a pause or a rise ends it, so noisy readings raise the count. A fall that runs across midnight counts once. Rainflow follows the three-point rule on a repeating day. Depth-weighted, rainflow gives the same energy as the equivalent-full-cycle rule when both use the same capacity.

Method: years to cap = cap ÷ (cycles per day × 365). Cycles per day = energy out ÷ capacity. The term and cap meet at cap ÷ (term × 365) cycles a day.