I did a fully factory restore of the iPad Mini 2 and following instructions for a battery calibration (a series of deep discharges and recharges). I installed only the essential apps to use the Mini as my drone only tablet. I had the mini hover in my living room and ran three batteries down from full to 20% and had plenty of juice in the iPad Mini 2 to do it. Thinking I had this licked, I tested outdoors today with a fully charged iPad Mini. After 15 minutes of flight, I had 78% on my iPad -- Until I shut it down and restarted. Then it showed 98%. I then flew for at least another 1/2 hour with my Mavic Air and now have 89%. So strange. I am going to keep doing deep discharges and full recharges to see if maybe I can reteach the iPad how to read the battery.