Try these 3 things (in this sequence):
1. New battery
2. New adapter
3. New motherboard (quite expensive!)
I only have my laptop for 1 year and 9 months. Recently, I noticed it charges up until 81%, then it says it's plugged in and not charging. It goes on charging more or less, but always with these pauses, which have become more frequent and not just at 81% like in the beginning. For example, right now it got up to 65%, stopped, charged 1 more, then again it stopped, and on and on it goes, it doesn't really have a definitive number anymore and the pauses can be for as little as 1% like I described or for more.
What could it possibly be and what should I do?