iPhone battery issues?

[Anoat]

My iPhone (5S if it matters) is going from 70% battery life to instantly dead. Can't turn it back on without plugging in the charger, and when I do, it comes back on at 35%. I've had this phone for about two years, so maybe it's just old and dying...any other ideas/fixes?

[Katlan]

Can be a buggy thing going in w/the firmware. Back up the phone and then wipe it back to factory settings. See if that fixes the problem

[ikariiiii]

if your phone is dying at high percentages chances are the battery is shot or the OS is unstable. go to support.apple.com and have them run a diagnostic on it (can be done via wifi since the diagnostic is through a server, not a wired connection).

if the battery checks out to be normal, you have to restore via itunes to factory settings and set up as new, don't use a backup. icloud can save a bunch of your stuff but photos you're better off saving to your computer. source: i fix these phones every single day