12.9-ich iPad Pro features as first iDevice Quick Charge. Your battery can be charged from zero to 100% more than 2x faster. But packed charger is only 12 W and it takes about 4.5 hours to recharge it from zero. If you want to use Quick Charge, you have to purchase 29 W Charger and USB-C to Lightning cable. If you have ultraportable MacBook Retina, you already got it. But some users refer, especially on iOS 10, that iPad Pro is discharging when on 29 W charger! What is it? How to solve it?
Now worries, in most causes it’s not hardware failure, it’s just software bug. I don’t know why is this happening. If you are charging iPad Pro and % are lower and lower, try hard reset – hold power off button and Home Button at the same time. You may need to do it 2 or 3 times, but after this battery % will be shown correctly.
Second way is just to left iPad Pro charging. You may experience battery’s %s drops for example from 95% to 87%, but after some time, it will fix it by itself.
This is strange bug, and if previous hints does not help, it may be hardware failure. As for me, I have never experienced this issue, if my battery level was under 80% when I began charging. And when I tried to recharge my iPad Pro via USB port in my iMac, I have never experienced this issue too.