Cycle Life

What the number actually claims

A cycle life figure is meaningless without three qualifiers: the end-of-life threshold, the depth of each cycle, and the test conditions. “800 cycles” tells you nothing on its own. “800 cycles to 80% capacity at 100% depth of discharge, 0.5C charge and discharge, 23°C” is a claim you can compare.

The 80% convention exists because lithium capacity declines gradually rather than failing outright. A pack at 79% is not broken; it simply no longer delivers the range the specification promised.

Why the conditions dominate the number

The same cell tested differently produces wildly different figures, which is why datasheet comparisons between suppliers are so often meaningless.

Shallower cycles extend life substantially — a pack cycled from 80% down to 30% will outlast the same pack cycled 100% to 0% by a large margin, which is why fleet operators who charge opportunistically through the day see better longevity than the datasheet implies. Higher C-rates and elevated temperatures both shorten it. Storage at full charge degrades cells even when they are not being cycled at all.

Chemistry sets the baseline: LiFePO4 typically offers several times the cycle life of NMC at the cost of energy density, which is the core of the NMC versus LiFePO4 decision.

Ask for the test conditions

Ask any supplier for the test conditions behind the number, not just the number. A figure quoted without a DoD and a temperature is marketing.

Then match it to duty. A consumer commuter bike might see 150 cycles a year, so 800 cycles is many years of service. A delivery fleet cycling daily reaches that in under three years, and the economics of a longer-life chemistry change completely. Tell us your cycles per year and we will size the chemistry to the replacement interval you can live with.