Chosen Solution
I changed my iPhone 4S battery, everything went fine but after like 2-5 minutes the phone shuts itself off. I took the new battery out and the old one back in and the problem is still there… It is really frustrating…
Sounds to me like the new battery isn’t calibrated to the device. What I mean is that the battery may think it is 100% full, but because the phone hasn’t gathered data such as the fully charged and fully drained point it doesn’t know where it is. It could read 100% but may actually be fully discharged. Turn it off and charge it overnight. Unplug it and plug it back in every once in a while during the process to make sure that the charger pumps a little bit more juice in each time. See if you can do a factory reset too, only after you try to charge it overnight though.
I’m having that same rebooting problem too after simply trying to replace a 2 year old battery. Every few minutes it reboots and it’s worse when it’s plugged in and charging. Has anyone figured out a fix for this that doesn’t require updating my version of IOS?
