battery-watt hours used

Discussion in 'iPhone' started by StaGro, Jul 9, 2011.

  1. StaGro macrumors newbie

    Jun 22, 2011
    I have the batteryLogger app (before it was removed from the app store) and it tells me my iPhone 4 (replacement from Apple store about 3 weeks ago) battery-watt hours used is 4.20. What does this mean? Is there an amount that should raise red flags?
  2. bandofbrothers macrumors 601


    Oct 14, 2007

    Im not sure but someone will be along to scare the crap out of you....only kidding.

    In my opinion some are getting way too caught up with battery juice !

    As long as mine gives me a full heavy days usage im just dandy.

    I want to use all the features on my ip4 and enjoy it, not dissect it !
  3. JulianL macrumors 65816

    Feb 2, 2010
    London, UK
    I believe that the capacity of the iPhone 4 battery is 5.25 watt-hours. To use a car analogy we can just pretend that a watt-hour is a litre of fuel from the fuel tank and the battery is the fuel tank in the car. That 4.20 figure is telling you that you've used less than a complete charge cycle (a complete tank of fuel) for whatever period BatteryLogger (BL) reports on.

    If BL resets the statistics after each charge then all that tells you is that on your last usage (charge) cycle you drained your battery down to 1.05 watt-hours remaining of energy in the battery before recharging it. (Note that the iPhone will power down before the battery reaches zero so that there is still some energy in the battery since batteries don't like being totally drained. The battery indicator on the status bar deliberately lies, 0% does not mean a totally drained battery as far as the internal electronics is concerned, it just means that it's got to a low enough battery level that the phone won't let the user drain it any further so it plays dead.)

    If BL is reporting the total figure since it was installed, and you installed it 3 weeks ago, then the figure seems very low because that would mean that you've used less than a single charge over a 3 week period. (Maybe that's why BL was pulled? Maybe there's a fundemental flaw in the data it reports?)

    - Julian

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