Asus ME302C tablet charging forever and doesn't start
I had the same problem and discovered the problem is the digitizer board which the USB is attached to. I found one on eBay for $60 dollars and like magic, in twenty minutes it went from 80 to 100 percent while it was in use. 

Out of desperation to fix my slow charging problem, I scoured the internet and one solution kept presenting itself, it's a hardware problem with the charging port. So I had planned to buy a new charging port and found them for under $7 on eBay. I don't solder very well, so I was dreading this process and then quite by accident I found the digitizer board which included a charging port.  I was stoked, no soldering. It worked like a charm. You can save yourself some money if you can solder by just buying the port or else get a digitizer board. The part no is CL-2E241819.