Samsung S3 charging problems

A

AC Question

Hi I have had my Samsung Galaxy S3 for over a year now, and the battery has been decent until now. It will be at 100% and drop considerably even though I am not on it. I always close all my apps down and the screen is always on the lowest setting and power saving is on constantly.

Last night is went from 86% to 20% in 3 hours, with no use and then went from 20% to 1% within 10 minutes, with little use. I then turned it off and when I turned it back on it said it was 57% and proceeded to freeze on me and refuse to do anything. I took the battery out and put it back in and it said it had 0% battery.

I am charging it right now and it went from 1% to 70% within less than ten minutes of charging, which is ridiculous. I have anther battery, a non genuine one in the post but I wondering if this one can be saved? Or if I can do anything to help it stay charged longer? I daren't use it because it drains so fast!