Chosen Solution
I have replaced batteries in both 4s and 5s models before with success. Currently, I’ve replaced battery in a 4s twice (both new batteries) but it will completely drain to 0% while sitting unused with no apps running, even in airplane mode. If both new replacement batteries were not faulty, what do you suppose could be the problem. Make any suggestions? I’ let you know if they helped. Thank you……. Reed in Richmond, VA. Tuesday, January 2, 2018 10:20:30 AM EST
Beyond the obvious “possibly defective batteries”, what could cause this is a partial short on the logic board. This could be caused by a defective subsystem, perhaps a camera or sensor, that is draining too much current from the battery. This could also be caused by an issue on the logic board itself that has the same effect on current draw. One way to troubleshoot this is to disconnect as many peripherals as possible to see if this still occurs. You could disconnect cameras and sensor and then test the device. If the phone behaves the same way with all peripherals disconnected, then it could be the screen or a logic board issue. Ultimately, if everything points to the logic board, then it will require more in depth troubleshooting by a micro-solderer. However, I doubt it’s economically viable for an iPhone 4/4S.
I would recommend not repairing a phone that old. If you are in desperate need of a new phone you could even get a 5s. This repair would probably cost more than the phone itself.
