Cycle life describes how many charge-discharge cycles a cell endures before fading, and the number means little without the test conditions behind it.

What Standards Are Used for Cycle Life Testing?

How Cycle Life Tests Run

A typical test charges the cell to its upper cut-off voltage, rests it, then discharges at a set current to the lower cut-off voltage and repeats, usually in a climate chamber held near 25 degrees Celsius. The test stops when capacity falls to a predefined threshold, commonly 80% of the initial value.

Why Conditions Matter

Results depend heavily on C-rate, depth of discharge and temperature, so the same cell can show very different cycle numbers under different settings. Manufacturers and buyers commonly refer to widely recognised battery testing conventions that define these reference conditions rather than one single universal number.

Always read a claim together with its conditions, such as cycles at a stated rate, temperature and depth of discharge down to 80% capacity; a bare number is not meaningful. Agree the temperature, rate, depth of discharge and end-of-life criterion during project evaluation. Testing is normally carried out on representative production samples rather than on a hand-picked best cell.