How do I optimise battery charging limit and cycle count on iPad Air M2 2024

The ability to limit charging to 80% of maximum capacity is only available for the most recent models of iPad - specifically the iPad Pro M4, iPad Air M2 and iPad mini A17 Pro. This support page describes how this your iPad's battery management works to reduce battery aging and to manage the charging-cycle.

Charge and maintain your iPad battery – Apple Support

You should note that to optimally maintain your iPad's battery - and maintain charging calibration - your iPad will occasionally fully charge to 100% even if you set the 80% charging limit.

Your iPad will suffer no ill effects through being connected to its Power Adapter for extended periods - and will automatically regulate and optimise charging. While connected to an adequate external power source that meets the immediate load-demand, the iPad will draw power from the external source - with occasional peak-load being supplemented by the iPad's battery, if needed, to meet the peak CPU/GPU and display power demand.

Powering the iPad in this way will reduce the amount of battery charging - and therefore reduce the rate of accumulation of full battery charging cycles. One charging cycle equates to any combination of battery charging that together sums to 100% (e.g. 10% + 20% + 20% + 50% = 100% = 1 full charging cycle). While you cannot fully avoid accumulation of charge cycles, you can substantially reduce the rate at which full charge cycles accumulate over time.