AAPL Stock: 118.03 ( -0.85 )

Printed from

Report: new iPad continues to charge after displaying '100%'

updated 11:30 pm EDT, Fri March 23, 2012

Testing points to bad calculation in algorithm

A leading researcher examining the third-generation iPad has discovered through testing and actual voltage readings that the latest iPad requires around two hours of additional charging beyond the point where the indicator reads "100%" in order to truly achieve maximum charge. Initial testing indicates that the problem lies only in the accuracy of the on-screen battery charge indicator rather than a hardware fault, but could lead to consumer confusion on performance.

Dr. Ray Soneira, president of DisplayMate and best known for running down the science behind the term "Retina Display" as used with iPhones and iPads, has continued his analysis of the latest model iPad and says that the tablet continues to draw a significant amount of power for up to two hours after "prematurely" displaying a full battery level. A faulty mathematical charge rate model could be behind the bad readings, Soneira hypothesizes.

Because of the new iPad's longer charging cycle, many users may rely mostly on charging the unit overnight or for longer-than-necessary times, since the unit will automatically reduce its power draw to nearly nothing once the unit is fully charged. The fact that it actually needs considerably more time than it appears could confuse customers who unplug the unit after it reaches 100 percent but don't get the longevity of battery life seen by those who leave the iPad on the charger until it reaches "trickle charge" levels and thus think their unit may be defective.

The charger normally draws 10 watts of power in order to recharge the battery as rapidly as possible, and in other iOS devices is often seen to draw the full 10 watts until it reaches an estimated 90 percent of full charge, then gradually reduces the draw for a short period until it finally drops to a one-watt "trickle charge" activated as the battery slowly degrades even when not in use.

It's possible that the mathematical model the indicator uses to guess at the battery's level hasn't been updated from the previous iPad, even though the new, larger battery offers 70 percent more capacity and thus requires a longer time to charge. According to Soneira, "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." If the formula used for the new iPad is incorrect, it would not affect the actual charging, but does prematurely show a full charge when in fact the device is still drawing power.

Some iPad owners have reported that normal charging appears to take around six hours, a considerable increase from the previous model. Many users will not be aware that the battery is physically larger than the previous model, being needed to drive the doubled resolution and more powerful processor and graphics. The latest iPad is only marginally thicker and slightly heavier than the previously model.

Soneira points out that most other mobile devices also "lie" about their true charging times, including both other brands and various Apple products. Largely this is less from malfeasance and more due to the way mobile devices calculate how long they ought to charge, which is what the indicator usually shows, rather than verifying that the battery is actually fully charged.

He calls for Apple to correct the issue, which can likely be mitigated through a software update. The fix may also determine if the battery indicator is inaccurate all the time, or just in the final stages of charging. The amount of time actually needed to charge the new iPad's battery is not the real issue, Soneira says -- but the indicator should not read 100 percent until the point where the charger drops to a trickle charge.

by MacNN Staff



    Comment buried. Show
  1. Thecombinationis12345

    Joined: Dec 1969


    comment title

    Apple should've delayed the retina display upgrade until the powerVR 6 series GPUs + Cortex A15+A7 big.LITTLE SOCs were ready next year. This new iPad is going to have a few more major issues before the year is up.

    Shoving a large hot SOC a few mm from a super huge Li-poly battery and hardly any breathing room? Bad internal hardware design.

  1. iphonerulez

    Joined: Dec 1969


    I think consumers will be

    satisfied with what they're getting now. There would definitely have been a lot of bitching and griping if the Retina Display wasn't ready for this model. The critics would have been "disappointed" that there was no high resolution display. The critcs don't give a damn if components aren't ready, they just want new technology now. If not for the Retina Display, what would this new iPad have to boast about it? For me, if Appl could have increased the battery charge 70% in the old iPad, I would have been happy. However, the tech critics always want more. This iPad may not have the best optimal hardware, but it's a decent stopgap model.

  1. jay3ld

    Joined: Dec 1969



    I am not sure if thats what the boss meant by giving it a 110%

  1. facebook_Katia

    Via Facebook

    Joined: Mar 2012



    There's a mistake in article. Sonera speak about "that the batteries do not

    actually reach full charge when 100% is shown and need up to an extra hour before the charging actually stops".

    1 hour, not 2 hour. It's a bit different.

  1. apostle

    Joined: Dec 1969


    iPad 1

    I have an original iPad. I've noticed that my iPad stays at "100%" longer, if it's been charged overnight (as opposed to charging for just an hour or two). I usually have it plugged in so this is really a non-issue for me. Just made me wonder...

  1. efithian

    Joined: Dec 1969


    100% +

    I took my new iPad for a drive the other day, using 4G(ha!), and google maps with hybrid view. When I started the drive the battery showed 100% after charging all night. After the 15-minute drive, the battery charge was still 100%. It should have been maybe 90-95%. Software update needed.

  1. sessamoid

    Joined: Dec 1969


    Most other tablets only to 100%

    This one goes to 111%.

  1. JuanGuapo

    Joined: Dec 1969


    Original iPad 3G owner.

    Charged to 100% and stays there for probably 10-15min after I take it off of the charger; it has done this since I bought it in 2010 on iOS 3. Normal.

    As for the charging of the new iPad, it's going to pull a charge after 100% because the iPad is still being powered over AC.

    Apple designs their own cells to last 1000 cycles, and you guys believe some clown who has something to sell? Didn't you learn from Antenna-gate?

  1. testudo

    Joined: Dec 1969


    Re: Original iPad 3G owner.

    Apple designs their own cells to last 1000 cycles, and you guys believe some clown who has something to sell? Didn't you learn from Antenna-gate?

    What's he trying to sell you? I see nothing here that says "The doc says the only way to currently fix this issue is to buy their product". He said "A software fix is needed". It's an information piece, nothing more.

    But, no, someone has posted something that isn't just bowing before Apple and their devices, so there must be some sort of bias or slant or reason behind it. Probably some android loving guy trying to start a fear that the iPad will catch fire in your pocket and burn your gonads off, or something. Yeah, that's it!

  1. testudo

    Joined: Dec 1969


    Re: Original iPad 3G owner.

    Didn't you learn from Antenna-gate?

    Yeah, I learned that a small group of people had issues with the antenna layout of the iphone that caused it to just disconnect on them when they held it a certain way (which, for them, was NOT odd, strange, or difficult to hold).

    I also learned that the Mac fanboy community is very vocal about any complaint and will attempt to shout it down as being overblown, overhyped, overreported, and a non-story, no matter how much information is out there. And then, when Apple basically admits there was a problem when the redesigned their antenna in the new iPhone, it's not because there was a problem. Nope! No problem, we know that, because Steve said so. It was just to shut up the complainers (who had long stopped complaining, but that's neither here nor there, either).

    Yep, that's what I learned. Apple makes perfect products, only apple-haters and/or droid lovers and/or ms employees can find fault with them, and only then by making up stories.

Login Here

Not a member of the MacNN forums? Register now for free.


Network Headlines

Follow us on Facebook


Most Popular


Recent Reviews

Ultimate Ears Megaboom Bluetooth Speaker

Ultimate Ears (now owned by Logitech) has found great success in the marketplace with its "Boom" series of Bluetooth speakers, a mod ...

Kinivo URBN Premium Bluetooth Headphones

We love music, and we're willing to bet that you do, too. If you're like us, you probably spend a good portion of your time wearing ...

Jamstik+ MIDI Controller

For a long time the MIDI world has been dominated by keyboard-inspired controllers. Times are changing however, and we are slowly star ...


Most Commented