he most likely cause of inefficient device charging is a bad connection between charging cable and the micro USB charging port. Try using a different charging cord usually fix the problem.You can purchase a new chaging cord here:
[http://www.astrogaming.com/accessories/3ACBL-HBM9U-745.html].
If the problem persists after changing charging cord, it is very likely that the connection between USB port and the motherboard is loose. Try soldering the USB port again based on the [USB port replacement|guide].