Why is my battery dropping charge

[AC Question]

the battery on my 8 7840 drops down to 30% normally then just drops to 0% and closes down the tablet This can happen whether i am using the tablet or just overnight

 

[B. Diddy]

Welcome to Android Central! How old is it? That can be a sign of a failing battery. But it might also be that the battery monitor software needs recalibration. Charge it up to 100%, use it until it shuts off, and repeat about 3 times. Now see if the battery monitor is more accurate.