ipad air m4 charging battery

Don't over-think charging of your iPad. Simply charge the iPad whenever the opportunity arises; your iPad can't be overcharged - even if connected to power for an extended period. Avoid unnecessarily discharging below 20% - and always recharge promptly if the iPad reaches a low state of charge.

As charge cycles inevitably contribute to reduction in battery health, reducing the frequency of charge cycles will extend the useful working lifespan of the iPad. Arguably, using the iPad while connected to its Power Adapter will reduce the need for recharge - and reduce the rate of battery health decline.

Information about iPad’s battery management can be found here:

About the iPad and iPhone charge-management feature – Apple Support

In more detail, "Battery health" is influenced by many factors...

An iPad battery is nominally rated to retain 80% of its original capacity (when new) after 1000 full recharge cycles. Any combination of charging that together sums to 100% equates to one full charge cycle (e.g., 50% + 20% + 20% + 10% = 100% = 1 full charge cycle). As such, reducing the number of times that the iPad is recharged will slow the rate that the iPad's battery health will decline due to recharging.

Other factors can influence overall battery health. High ambient temperatures can permanently reduce the battery's ability to retain full charge - as can maintaining the battery at 100% charge for very long periods of time that leads to chemical aging of the battery. Limiting the battery charge to ~80% of maximum may reduce the chemical aging effect - but will inevitably result in the iPad needing to be recharged more often when utilised with battery power alone.

Independent studies have demonstrated that routinely restricting charging to only 80% of maximum has little if any impact upon the overall longevity or health of the iPad's battery. There is no need to micromanage your iPad's charging strategies.