Why does my samsung galaxy SIII mini shut down when it wants to?

[AC Question]

My Samsung Galaxy SIII mini has a battery life of about lets say..95% I open a game like Clash of Clans.. like about 5-10 minutes after I open and play, the phone shuts down itself and when I turn it back on, the battery has drained to like 30-45 %

And sometimes when I restart my phone manually when the battery is at like 75%, when it turns back on, the battery is like 85-90%

I have only rooted my phone and I am wondering if it is the rooting which did this or is it just my battery as this phone is about 3-4 yrs old..

Pls Help! THANKS!!!

 

[the tall guy]

Hi - I would put it down to being your battery and the fact the phone is very old. Try replacing the battery and seeing if this helps.