I had this same thing. The Batter image had a red line on the right side and the yellow triangle had an explanation point in the middle.
I searched the net and found a few solutions.
1. Hold the power button down for 30 seconds.
2. Hold the power button down and the volume down button at the same time for 30 seconds.
3. Just let it charge and over night and it should go back to normal.
I did all 3, in the order I wrote them. While in step 3, after about 5 minutes I pressed the power button and it showed that it was charging normal.
Hope this helps.