iPhone shuts off when battery is at about 20% I have an iPhone 4S running iOS 8.0.2. For the past few days, my phone has been shutting off when the battery reaches around 20%. It will not turn back on until I plug it into a power source. When I plug it in, it automatically powers itself on, and the battery shows about 20%.

This is my battery info:


CycleCount: 298
DesignCapacity: 1430
FullChargeCapacity: 1000
Status: Success
BatteryCurrentCapacity: 72
BatteryIsCharging: true
ExternalChargeCapable: false
ExternalConnected: true
FullyCharged: false
GasGaugeCapability: true


Questions: does anyone knows why this is happening, and how can I make the battery function until 2-4% like it used to before?
I attempted someone else's suggestion to let the battery naturally die off (let something running without actively using it), then charge it back until 100% without unplugging. The first time it did not work, but after I did that for the second time, my phone is back to normal. So... I just needed to be patient I guess.