Why is my battery not working?

[AC Question]

Okay so I have a Samsung Tab 3.8 and for the past month it has been acting up. For example when I charged it last night, it would stay at 0% but when i take the battery out and charge without the battery it jumps to 71%, and also it has been charging extremely slow before I change the charger, than it'll charge extremely fast before going slow again days later, please help me solve this issue.

 

[B. Diddy]

Welcome to Android Central! Are you opening the tablet up to remove the battery? It's not normally user-removable.

If you can, replace the battery, since it might be failing.