There are a few things that it could be. As others have said, it could be the battery, charge port, or cable. On mine, however, it was the charge circuit on the motherboard. Mine was refurbished, so it didn't have a warranty. So I opened it up and saw that the solder work was supremely sub par. There were about 3 or 4 diodes that were far enough away from the solder pad, that they eventually lost connection. It could have been from the board flexing or from heat. Either way, I added a big solder blob to anything that wasn't perfectly centered and it worked again. I am actually thinking about trading mine in for something else.