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.

  • Completely discharging the battery and then fully recharging is called "deep cycling". You can read about it with the search deep cycle battery. I know its used with lead-acid batteries to help them "forget" its charge. I did not know it worked with lithium-ion batteries. – user83961 Mar 27 '15 at 5:22
  • @jww: More likely the answerer just recalibrated the component of her phone which looks at the battery's voltage (and maybe other factors?) and displays a "percent of battery remaining" value. – unforgettableidSupportsMonica Sep 11 '15 at 11:56

Two likely solutions:

1) Change the battery. 2) Backup & restore.

It is unlikely to be a software problem, considering the circumstances; so there's probably not much you can do without a screwdriver. Just in case, try 2) first and if that doesn't work, take it to an Apple store, and get it looked at by an Apple genius. They will either offer a new phone, or change the battery. Both will cost unless you have a warranty.

Good luck!


I keep fully charging my iPhone 4s and using it throughout the day. Every couple of days my phone is dying at 7% 20% etc. I have researched this and many people are experiencing the exact same thing. The same percentages and are fully charging it! I think it is just a problem with iPhone 4s'due to reasearch.

My phone was second hand and off eBay and someone I know had the same problem with theirs. It is definitely a big problem with iPhone 4's and 4s'.


  • Are you saying people expecting used batteries that are three years old to be fully functional is the problem or that you can't find someone that can help you diagnose and service batteries is the problem? Could you edit your answer so it makes sense as an answer to the question? – bmike Nov 15 '15 at 21:39

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