As crazy as it sounds, if you heat a dead Ipad (Air 2 in my case) over the stove until it is hot to the touch, it will begin to charge a completely dead battery.
First, I got a sustained 2% charge and left it overnight only to find it was stuck at 2%.
Heated again, then 12% and stuck there.
So continued the process up to 100% (heating every 30 minutes) and now the ipad is fully recovered and can drain and recharge as normal.
