Chosen Solution
Hello, I have a customers 7+ here which we initially replaced a battery on due to poor battery life. After the initial battery replacement, the customer returned within the week with the device not charging past 8%. Replaced the battery under warranty, which seemed to resolve the issue, however the device was gaining percentage rather slowly. Replaced the battery for a third time to good result. Customer returned with the device not booting past the apple logo. Replaced the battery again (!) in an effort to be thorough, and performed a factory reset. Device charges normally (0.9amp) seems to hold charge fine, but now the customer has returned with the device spontaneously rebooting at any percentage below 90%. Performing a DFU reset, before giving up and sending it to a microsolderer. Does anyone have any insights? Greatly appreciate your time. Thanks.
I would inspect the logic board near the battery connector. There are several (tiny) passive components there including a resistor (R2201) that is on the line that communicates the battery status to the CPU. If this part gets damaged or dislodged, then it will give you the same symptoms.
This also requires a micro-soldering repair.
