Chosen Solution
Hi, Mint condition red iPhone 8 iOS 13.1.3 , had a dead battery which we replaced with a new battery and the phone worked fine for multiple days. Phone randomly rebooted and now will work perfectly just reboots itself at random intervals. Ive tried a different OEM battery, known good and it does the same behavior. I tested the battery connector for the correct meter readings and the readings match my known good iPhone 8 boards. Also visually the phone and mother board are in mint condition so Im not sure what could be damaged. Aside from simply replacing the battery, we also removed the foam pads around the two connectors for the LCD to allow for a better connection. Again, the phone works flawlessly it just has a random reboot issue and Im not sure what is causing it. I have considered replacing the charge port but the phone is pulling normal amperage.. any ideas?
The IPhone 8 will show symptoms like this if it has a faulty gas gauge circuit. It will reboot because it cannot determine the battery condition. This can also be caused by the battery FPC connector. I know you have checked that but I wouldn’t rule it out on the IPhone 8. This is one of those difficult repairs; I would start by checking your gas gauge circuit with a known good board. You might pick up a slight variance in diode mode. That is about all you can do besides swapping chips out.
