Phone battery charging at around 60% but 9% when I shut it off while charging?

[AC Question]

So I'm charging my phone at around 60% a pretty high percentage, but it was taking so long to charge so I switched it off leaving it plugged in. Whenever my phone is plugged in while switched off, it shows the battery percentage which then shows as 2%. Why does my phone battery go from 60% to 2% just from switching it off? Is it something wrong with my battery? Does it need calibration?

 

[chanchan05]

How old is the battery since you first used it?

 

[B. Diddy]

Welcome to Android Central! I agree with what chanchan05 is implying -- the battery might be failing, especially if it's old. Which phone do you have? Does it have a user replaceable battery?