Why does my phone die at a very high percentage?
For a while, my phone has been gradually increasing at when my phone would die.
(eg, a month before my phone would die at around 40-50%, now it dies at 90-100%)
This happened a while ago with the same phone and some how, my phone fixed itself (I don't know how it happened) and it went back to normal (dying at 0%). But, the problem repeated again and I've tried everything (DFU restore, discharging and leaving it overnight) and my last resort is buying a new battery or even a new phone.
I've seen some posts where people say you run a battery-intensive app and let it discharge until 0%, but it's impossible for me, since I can't reach even below 50%.
When it dies, it stays at the flat battery screen and will instantly reboot once a charger has been plugged in.
Info about my phone:
-Bought my phone from a friend
-I have gotten the battery replaced, so my warranty is voided
I would like to not buy a new battery, as it costs a lot of money.
Suggestions thanks :-)
(edit- when I reboot it, it goes to a different battery percentage, different to when it died. eg it died at 100%, but when rebooted it shows 96%)