As we told you last week, unplugging your brand spanking new iPad as soon as the battery gauge hits the 100 percent mark entails missing out as much as ten percent of additional run time, or about 1.2 hours. This has been attributed to the iOS battery algorithm, which kinda brings back old memories of a bug in reporting cellular signal levels on the iPhone 4, later fixed with a software update.

According to new findings, this is actually a system-wide behavior in Apple’s mobile operating system – thus affecting older iPads, as well as your iPhone and iPod touch. In fact, all iOS devices are affected by what’s been called “busted” battery algorithm, it’s just more pronounced on the new iPad due to its 70 percent more capacious battery.

What exactly is going on here, you ask…

According to Adrian Kingsley-Hughes over at the ZDNet blog, this behavior has persisted in iOS and is actually affecting all iOS devices rather than just the new iPad. He thinks it’s by design: Apple is displaying the 100 percent charge indicator at a lower capacity of around 97 percent in order to keep the battery “safe and healthy”.

The author explains:

The battery on the new iPad is huge, with a total charge capacity of a massive 42Wh or measured another way a monstrous 11,666 mAh. A 3 percent safety margin for the iPad 2 battery would be equal to around 210 mAh, while the same safety margin for the new iPad would be equal to 350 mAh.

The crux?

The wrinkle is that when the iPad 3 battery indicator first says “100%,” the battery is actually only 90% charged and you get 1.2 hours less running time. However if you recharge your iPad 3 unattended (and off or in sleep mode), especially overnight, you will get the necessary extra charging time to achieve its maximum running time.

According to DisplayMate, the device takes over 5.5 hours to fully charge when off or in sleep mode and up to a whopping 20 hours with the display set to maximum brightness. Recall, if you will, that DisplayMate also blamed the iPad’s Retina display with twice the LEDs for shorter run times and the widely reported overheating issues.

Now, here comes the really interesting bit.

Perhaps not surprisingly, Soneira might have damaged his own reputation by stating Apple’s supposed claims of how overcharging your new iPad allegedly could hurt the battery inside. Strangely, Dr. Soneira did not provide a link to Apple’s website proving this.

According to Apple, the new iPad is configured to damage the longevity of its own battery if it isn’t manually disconnected from the AC charger when the 100% indicator appears. Anyone that recharges their iPad unattended, especially overnight, will be doing this. While Apple’s remark might apply to recharging dumb battery operated toys, the new iPad is a very sophisticated and expensive computer device that is fully capable of properly controlling and managing its own (rudimentary) battery charging process.

Information provided on Apple’s website makes no mention of any of this and Dr. Soneira backtracked later. Meanwhile, CNBC relayed Soneira’s logic and said overcharging will actually harm the longevity of the battery.

I know what you’re thinking, big media, right?

Indeed, one would think CNBC should exhibit some expertise about how lithium battery technology works. The charging circuitry in lithium batteries prevents damage by automatically halting the charging process once the battery reaches its full charging capacity, putting it on a trickle charge that keeps the battery at or near 100 percent.

Batteries Apple puts in its iOS devices typically supports up to a thousand full charging cycles. Afterwards, the battery capacity slowly begins to diminish over time. The company educates customers how “a properly maintained iPad battery is designed to retain up to 80 percent of its original capacity at 1000 full charge and discharge cycles”.

I don’t know about  you, but I’d expect the iOS battery gauge not to lie about charging. I mean, a 100 percent should always be a 100 percent, right?

  • so… what’s the solution for the “problem”?

    • Anonymous

      They never provide solutions. They only rehash what someone else theorized without ever testing it for themselves – Most, if not all, of these are reported as fact.

      Later in the day they will update the story after the original author backpedals when the story gains national attention because someone has proved him to be clueless.

      Steve Jobs said he doesn’t want to see us descend into a nation of bloggers, this is why.

  • Anonymous

    Interesting. I wonder how much this applies to the iPhone 4S battery

  • what i cant stand is, going from 100% to 90 percent takes a long time but when you get to 20 or so percent it drops so fast. it has made me feel, since 2007, that apple made an algorithm that makes it seem that iDevices hold charges better than other devices. but i just can’t find anyone else to agree with me :-s

    • My thoughts exactly

    • I get the opposite. The first 30-40 drops fast, and when I get to ~20 it sudden last an age, compared to the low number.

      • which device do you have? i had ipod touch 1G, iphone 3GS, iphone 4Sucks and iPad 1G and they all had the same battery behavior.

  • Can we expect a software update to fix the problem? The new chip and retina display clearly use a TON of power, because even with an upgraded battery my new iPad still dies faster than my iPad 2. Listen to this…. I was watching Netflix at full brightness while the iPad was plugged into my computer sharing, the batter STILL drained at a FAST rate. Is this the 90’s?

  • Caio Falasqui

    every time im charcing my ipt4,hwen gets to 100% and i take off the charger,shows 95%

    • Same on my brothers iPod Touch 4g, but it goes to 94%

  • Anonymous

    I’ve noticed with cydia tweaks that can hide and show the battery meter they often are a few percent lower or higher than the default iOS meter and I’ve always wondered which is more accurate

  • Just get Battery Doctor and solve all your battery related issues.
    It charges the device and then does a trickle charge to top it off.
    I regularly let my battery down to under 10% before I charge it
    (iPhone 4 and iPad 2). They battery lasts quite a while for me
    on both.

    • Metroview

      As if an app, AN APP, will help your battery life. An app doesn’t recharge your device. Last time I checked, a USB cable and dock charged my phone.

      Maybe I missed something but i’m pretty sure that’s how it works.

    • Anonymous

      Those apps do nothing other than give you statistics. Software cannot change physical attributes.

  • Anonymous

    Also Zidberg stop being such a blatant fanboy in your articles.

  • If you download the app Battery LED it says this, and it even says keep it on charge for another 30/40 mins.. to get the full 100 percent..

  • Sorry but this is a dumb finding… If you own an iPhone you already know when the plug icon comes on the battery then you know it’s about 100% and left longer it does hold battery longer.. That’s what I think

  • On iphone if you charge 1 hour its at 100% but apple call it a fast charge… 4 hours is needed to fully charge an iphone … On ipad 2 it takes so long to get to 100% i dont think there is this “fast charge” process. So on ipad 3 i think they try to bring back that “fast charge” for just make people think its 100% faster so there happy …. But thats my opinion … Just sharing

  • Apple will fix it eventually, the media focuses to much on the negative side of apple, and not enough on the positive side.

    And isn’t the ipad doing many background tasks as it charges such as iCloud backup etc…

  • Anonymous

    me ipt4 battey goes for about 6 to 7 hours untill that deredded 20% marck then its like a veyron at top speed vglug glug glug ihate 20%

  • i hate the battery>>>:(

  • I have noticed this on my iPad, and it seriously made me think my battery was nearing the end of its life (as with my iPod touch 2g, which shows 100% and then jumps to ~95% when I unplug it)


  • I have noticed this on my iPad, and it seriously made me think my battery was nearing the end of its life (as with my iPod touch 2g, which shows 100% and then jumps to ~95% when I unplug it)


  • Don’t know about the iPad3, but I can tell you what for sure modern computers and supposedly smartphones, tablets or any other modern devices do:

    When they reach the maximum charge, AC is disconnected to avoid battery overcharge, thus allowing it to discharge a small percent just to reconnect a bit later and recharge again. This is great to avoid the battery quickly wearing due to overcharge, which I suppose DOES NOT happen on an iPad or iPhone. But it still consumes battery cycles (which are limited, in fact they are a good measure for a battery’s lifespan) so eventually you end up wearing the battery anyway (but slower).

    Bottomline is that damaging the battery whilst charging overnight can NOT be avoided, but it’s not due to Apple’s fault nor exclusive to the iPad. This is quite widely known. Apple itself claims this in their laptop battery information pages (or at least used to some years ago), so that is probably what (intentionally or not) Mr Soneira was (erroneously) referring to.