Re: My legoion y720 apperats to be conected to the ac adapter but it is not charging
Your laptop doesn't want to keep the battery at 100% - It'll quickly degrade your battery over time. While plugged in, it'll stop charging the battery and have it drop a bit once you reach upper 90s or 100%.
This is normal and is to allow longer battery life. Your battery shouldn't fall lower than 90% while plugged in.