iPad 3: Explanation of the charging after 100% issue

iPad 3: Explanation of the charging after 100% issue

Summary: The iPad 3 battery continues charging even after it reports that it's "100%" full. In reality, it continues to charge for another 2 hours and 10 minutes.

TOPICS: iPad, Hardware, Mobility

Early yesterday Macrumors reported that the iPad 3 battery continues charging -- even after the menu bar icon reports that it's "100%" full.

Ray Soneira, President of DisplayMate Technologies Corporation, took a deeper dive and discovered that the iPad 3 battery isn't fully charged until 2 hours and 10 minutes after it says so.

The charge indicator on all mobile devices is based on a mathematical model of the charge rates, discharge rates, and recent discharge history of the battery. It uses this information to estimate how much running time is left. It's actually rather difficult to do because most batteries degrade slowly as they discharge and then tend to surprise with a precipitous decline near the end.

So there is something wrong with the battery charge mathematical model on the iPad. It should not say 100% until it stops recharging and goes from the full recharging rate of about 10 watts to a trickle charging rate of about 1 watt. Otherwise the user will not get the maximum running time that the iPad is capable of delivering, which is listed in my iPad shootout article.

Soneira's final results:

At 2:00 hours after reporting 100% charge the new iPad hardware started to reduce the charging power. At 2:10 the recharging cycle fully terminated with a sharp decrease in power.

The new iPad battery is truly fully recharged 2 hours and 10 minutes after prematurely reporting on screen that it was fully charged.

I'm guessing that Apple will fix this in iOS 5.1.1?

Topics: iPad, Hardware, Mobility

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  • You're late to the party, Jason

    SJVN already beat you with this report.
  • guessing that Apple will fix this in iOS 5.1.1

    Nope. There is nothing broken other than people's knowledge of battery technology.

    A fix would be to let the indicator tell you that it takes 2 hours to complete the last couple percent of charge capacity, which will end up in yet another batterygate.

    Besides, it's better for this battery technology to not be peaked at every charge.
  • Do you lose another 2 hours of battery life?

    Without the 2 hours extra charge, do the ipad 3 lose 2 hours of battery life?
    • No...

      No. With modern tech (not just the iPad - laptops also do this) charing starts very fast, but slows as the battery approaches "full" charge. This is deliberate, a designed to minimise the impact on the battery's ability to hold its charge. The last part of the charge cycle his a much smaller impact on the battery's than the first "fast charge". This is why manufactures often quote figures to 80% charge (Lenovo do this on their fast charging ThinkPad).
  • I doubt they will, as it will be much easier to fix this

    in the PR department.

    Apple will just claim that it is so magicaly advanced that there is no mathematical algorithm in existence that is capable of accurately tracking the charge rate.

    The press will blindly agree, and the purchasing public will be relieved to find that they indeed were not charging it wrong.
    Tim Cook
    • Sorry mr Spock

      My iPad is not that precise and I hit the - when I was aiming for +. Add 2 to your current rating.
      • But you don't have an iPad

        So your statement is irrelevant.
    • Heh!

      That's actually more true than you realise. The charge rate depends on a lot of factors, and the the system adapts its rate of charge while charging.

      This is true for devices other than the iPad too (and not just Apple). This is why you don't see devices show time estimates very often, and those estimates (when you do see them) are not particularly accurate.

      Magic isn't required, just physics.
  • And yet people will buy it blind

    PR at Apple is strong... people still buy Apple products blindfolded... even if products got issues....
    • More like...

      If people bought it, obviously they still found it more suited to their needs than any other tablet.
      Michael Alan Goff
  • ipad 3 charging issue

    i got new ipad when the day ipad 3 release to the masses (march 16). my concerned about charging it took me more than 8hrs before it fully charge, isnt it rediculous? what do u think guys, do i need to return and get to change another one? coz i doubt if theres a defect on this ipad...:(
    • Overnight?

      Can't you charge it overnight? (You do sleep - right?)

      Wouldn't that be convenient?
  • Power Drop

    If the hardware is "clever" enough to drop the charging power when the charge is complete, surely it's not beyond the software to detect this, and only say it's "not charging" when the power drops.
  • This doesn't add up!

    I suspect we're seeing a red herring media beatup here. If you could knacker your battery by leaving it on for an hour past full charge, it would be nigh on impossible to safely charge any battery that wasn't fully discharged at the start. If you had only used your iPad for half the day but needed it fully charged for tomorrow, you'd need to wake up every half hour during the night to check the state of charge. And the same thing would presumably apply to all lithium battery devices.
  • Battery apps

    I have several battery apps for Ipad and Iphone and they charge in 3 stages-fast, slow and trickle [ they call it full, normal and overcharge]. They call it a full cycle charge.