Chosen Solution
I’ve changed my iPhone 4S battery with an iFixit battery last April. Since then my phone keeps shutting off at 20% battery or above. (Most of the time between 25% and 35%) I have checked the status of the battery with iBackupBot and everything is fine. I have restored the phone. Dis-charged it fully and recharged it fully multiple times. I have tried discharging it and plugging it back in for a few minutes and then let it discharge again. I was hoping that the phone would “learn” about the new battery over time and that it would end up calibrating itself. But nothing has worked. Is the iFixit battery a dud ?… Please help.
Contact iFixit and ask for a replacement.
It does sound like a bad battery to me. I would try another battery.
