Dell Precision m4700 Plugged in, not charging

Less than a year ago, I purchased a Dell Precision m4700 laptop refurbished through Best Buy's online website. 

Recently, it charges to about 70% then switches to "plugged in, not charging" 

I've tried resetting and doing the thing where I take out the battery and adapter and hold down the power button- I'm thinking it's either an adapter or battery issue, but before I purchase anything I want to see what others think, so I'm not spending money unnecessarily