Cycle Aging
Cycle aging is battery degradation associated with charging, discharging, and the resulting energy throughput.
What counts as cycling
Cycle aging is linked to how much charge and energy move through the cells, not simply how many times an EV is plugged in. Several partial cycles can add up to an equivalent full cycle, while one deep cycle and several shallow cycles with the same total throughput may not produce identical wear.
The rate of cycle aging depends on Depth of Discharge (DoD), charge and discharge current, temperature, state-of-charge range, cell chemistry, and rest periods. Fast charging is therefore only one part of the load history. Capacity loss and resistance growth can develop at different rates.
Cycle aging overlaps with calendar aging because time-dependent reactions continue while the battery is being used and between trips. A vehicle's measured State of Health (SoH) reflects their combined effect, so real-world data cannot usually assign every loss to one mechanism with certainty.
For the detailed mechanisms, see Battery Degradation.