Apple's ipad air takes four to five hours to fully charge and can be recharged as you go. It is not necessary to discharge 100% before charging. Apple lithium-ion batteries work in charge cycle mode.
1: If the amount of electricity used (discharged) reaches 100% of the battery capacity, a charging cycle is completed, but not necessarily through a single charge.
2: For example, you might use 75% of your battery during the day and then charge your device fully during the night. If 25% of the electricity is used the next day, the total discharge will reach 100%, thus completing a charging cycle in two days. It may also take several days to complete a charging cycle.
It should be ready in about two to three hours