Turns out it was a bad charging USB cable. I was using the one that came new in the box, but it was defective. I had it charging all night long and the next morning it was only to 84%. I switched to a cable I had and then it charged quickly.
I am having the same problem. I just charged mine for several hours and it only got to 35%. I've only had it for less than a week. I'm using the charger that came with it.