This did it for me -Re: Why is my iPhone charging slower since updating to iOS 8.4?
Total reinstallation- That did it for me!
My heavily used ipad air had begun to either not charge at all or do it so slow, that it actually still lost power if I used it while charging.
I tried several different brands of cable and even more different chargers. Nothing helped, and I started looking for a replacement. Since it had been in action 5+ hours daily in 18 months, I figured it was ?used up?. But as a last attempt I did a total reinstallation. Made my backup copy, and wiped the ipad clean.
And voila! ! Now it works perfectly again. Charges as fast as the first day.
I hope it can help some of you who has this problem.