very slow charging
My macbook air has suddenly had 2 episodes of blackouts yesterday the battery was 15 % at that time. I had reset SMC and PRAM (as given on many discussions). Today I am facing this problem that my macbook air is not charging properly though showing connected it is showing 6 hour 15 minutes to full charge(@ 62 %. From 29 to 39 % it was fast then it slowed. I had put to the system sleep then after 45 min it is 62% and after that it is stuck or rather increasing % by % in 5 to 10 min. now at 64% it is saying 7 hour 12 minutes to full charge.
Please advise.
MacBook Air, OS X Yosemite (10.10.3)