Why is my Samsung Tab 3 battery draining so quickly?

[AC Question]

This morning i had just turned my tablet on after it charged all night,
after 20 minutes of use it was at 20%. why did it drain so quickly

 

[B. Diddy]

Welcome to Android Central! Moved this to the Tab 3 forum. Did it start at 100%? Has the battery been acting oddly for a while, or was this all of a sudden? If the battery continues to behave oddly, it might be failing.