Is my phone dead or just the battery?

[Lucas Kroon]

Hello. I have a Samsung Galaxy S4 Mini. I've had the phone for 3 years now. As expected, the battery drains faster than when it was new.
However, i am experiencing a new issue that leads me to believe my phone might be broken. The phone randomly shuts off or restarts itself without warning, even when the battery is at 90%. When it has been restarted, it sometimes dies immediately after i touch the screen. Only when the phone is fully charged it won't die.
When the phone is charging it does not die.

I've tested spinning the battery on a flat surface and it appears to be bulged.

My question is, should i buy a new battery or a new phone? I want to use this phone for maybe an additional half year, it works great apart from it dying.

 

[B. Diddy]

Welcome to Android Central! Moved from the S4 forum to the S4 mini forum.

That is almost certainly a dying battery. It doesn't have to bulge to fail. The easiest thing to do is to try a new or different battery.

 

[Lucas Kroon]

I got my new battery now. I've been using the phone for a couple days now without it shutting down on me, so the old battery was the reason the phone was turning it self off. Thanks for helping me take the decision.