iphone 5 - battery trouble
Hello.
I newly bought a used iPhone 5, knowing that it had som trouble with the battery indicator. The battery % indicater shows wrong, until the phone shuts down, and then restarts. To me it seems like a short curcuit.
This only happens when the screen is on, but if I keep turning the screen off regularly this won't happen. I've tried to turn off the battery % indicator, but there's no change. I've also tried to reset the phone, without any changes in the result - it keeps shutting down.
What can I do? Would it help to change the battery?
iPhone 5, iOS 8.4, null