I recently installed iOS 7 on an iPhone 4S. Does the Battery Usage/Percentage (as shown in the top-right corner of the screen of the phone) need to be calibrated again (by letting the battery fully discharge once, possibly to be followed by a full charge and a hard reboot)? Or is this nonsensical advice?

  • @Buscar웃 I've seen such advice multiple times in the comments on iphoneclub.nl (a Dutch iPhone website).
    – Řídící
    Commented Sep 24, 2013 at 19:02
  • @Buscar웃 Perhaps you are right. But even on this site you can find a similar comment. (Although the comment doesn't really specify that calibration would be needed for the % display.)
    – Řídící
    Commented Sep 24, 2013 at 19:13
  • @aufkag The calibration process does helps with % issues. Here is an answer listing the process. I don't think it's required in your question's terms, but should definitely do it if you're finding evident discrepancies.
    – Thecafremo
    Commented Sep 24, 2013 at 19:33
  • 1
    @Thecafremo It would be helpful to know and understand what is happening to recalibrate, since the % is only a mathematical product of the draw current vs Battery charge.
    – Ruskes
    Commented Sep 24, 2013 at 19:48

1 Answer 1


Discharging the battery once in a while (every few Months) is not a must but does help calibrating, for the system to be more accurate waring you on low levels.

Over time charging and discharging creates a more inaccuracy of the actual level. For example if you plug in at 40%, unplug at 80% and so on.

The reason is that the system uses the last known battery charge to produce the %, thus assumes the battery charge level.

However if the battery was not discharged for long time, the remaining charge could be wrong (due to batter aging).

Discharging to not less than 20% once in a while helps the accuracy.

Since there is a opposite effect (to frequent full discharge) will shorten the battery life, you should only do this every few months.

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