Why the new iPad battery meter is behaving just as it should

Why the new iPad battery meter is behaving just as it should

Summary: Batterygate. What Batterygate?

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Dr. Raymond Soneira, president of DisplayMate, the world's leading display and display tuning company, claims that there is a problem with the battery meter on the new iPad, which continues to charge even after reaching 100% and require an extra hour of charging to reach full capacity.

Actually, this is nothing new. Almost all devices powered by lithium-ion batteries exhibit this behavior, and it's only noticeable in the new iPad because of the huge battery pack it contains.

Here's the deal. The charging circuits inside modern consumer electronics are highly complex. They need to be, because the last thing you want to happen is to overcharge a big lithium-ion battery pack and have it swell up inside a device -- or worse still, overheat or possibly catch fire.

Charging circuits employ a number of tricks to help keep the battery safe and healthy. The first trick is to slow the rate of charging as the battery reaches its full capacity so as to avoid the risk of overcharging. You can actually see this in action when you change something up. You can notice how charging from 95 percent to 100 percent takes a lot longer than charging from 50 percent to 55 percent. This is deliberate and its purpose is to protect your battery - and you - from damage.

Another trick is set the 100 percent charge mark at a lower capacity, say around 97 percent and then have the charging circuit silently charge this remaining 3 percent while the device is still plugged to the charger. It's possible to see this in action too. Charge up you phone, but disconnect it as soon as it hits 100 percent charge and notice how fast it drops to 99 percent. Now charge it overnight and see how long it takes to drop to 99 percent when off charge. You'll notice that it takes a lot longer. It's a lot like filling your gas tank to the brim, it takes longer for the needle to fall from the full mark than it does is you don't fill it all the way to the brim.

Why are people seeing this with the new iPad but didn't notice the effect on other devices? Simple. 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.

My guess is that Apple will be able to tighten up the charging mechanism on the new iPad through a software update, but as long as you leave your new iPad plugged in for a bit longer, you should get the battery up to full capacity.

Batterygate. What Batterygate?

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Topics: Apple, Hardware, iPad, Mobility

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58 comments
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  • What???

    What does that have to do with the meter reading 100% When there is 20% remaining to be charged? I understand protecting people but you could do the same with an accurate meter.
    slickjim
    • Terms of unendearment

      What is "accurate"? Does "100%" mean, "the batteries cannot hold one more mAh without exploding, and even though charging to this level harms the battery, we don't want to give Peter Perry any excuse to call us inaccurate, so this is where we set 100% on the meter."

      Or does 100% mean, "this is about as much as you should charge a lithium-ion battery if you want to maximize its life, so even though the battery could tolerate being charged even more, we're going to tell you it's at 100% in the hopes that you'll stop here."
      Robert Hahn
      • I dunno

        Why don't I sell you a cup of coffee that is 60% full and tell you that is what we consider 100%!

        You can try to be slick all you want but your argument is flawed...

        Toyota maintains the Prius battery between 40 and 60% because it optimizes the life of the battery... When the battery hits. 40% it starts to charge and when it hits 60 it stops charging.

        Basically, if 80% was supposed to be 100% then Apple would have likely built something in to stop it from charging but, the battery continues to charge and thus, you have your answer!

        100% is when the battery is full to allowed capacity period!

        And this is the problem with you guys, this is not a major flaw but you would rather make like it doesn't exist and Apple is perfect rather than just say, no big deal. My issue is not with the flaw but with articles like this that try to pretend we are all just idiots.
        slickjim
      • I'll set my alarm for 2AM

        "so even though the battery could tolerate being charged even more, we're going to tell you it's at 100% in the hopes that you'll stop here"

        So Apple expects me to wake up in the middle of the night to watch the battery meter creep towards 100% and the moment I see that happen, I'm expected to unplug the iPad?

        I don't have to do anything so silly with my iPad 2. The reasons for not buying the new iPad are just piling up.
        toddbottom3
      • Where I get my coffee I get FREE refills:)

        Peter Perry

        So again don't see the cup full or not as an argument to be made. That and do you have any idea how difficult it is to add cream to a full cup of joe?

        Pagan jim
        anonymous
      • Engineer and market the battery so it is safe.

        I think Peter Perry up here has it right. What these companies need to do is engineer the battery and charging mechanism so that the capacity is larger than it needs to be. Market the battery so that when the charging mechanaism states it's 100% full, it lasts as long as it should per the marketing specs. This will also keep the battery from overcharging and blowing up and will also increase battery life.

        Sounds like the perfect solution to me. Build in a buffer.
        Archivedbyte
      • That 60% full cup of coffee is less likely to get cold as you drink it...

        Compared to a too full cup that's cold by the time you hit bottom. Or haven't you noticed the waiter/tress tends to refill you all too soon, diluting your cream and sugar?

        Really it's your argument that's flawed because no two battery types act exactly the same. Even lead/acid batteries come in Automotive and Deep Cycle Marine forms, one intended to be run to nearly dead on a regular basis while the other carries a very limited life when deep cycled. I might note you really don't know how the Prius operates its batteries while I've watched the system frequently; it recharges the battery every single time the engine has excess power to spare--it doesn't wait until the battery drops to 40% or lower before starting the engine. The Volt, on the other hand, does.

        @archivedbyte: Don't you think maybe that's what Apple is doing with this battery? It seems quite logical that they've built in extra capacity for simple safety's (and longevity's) sake.
        Vulpinemac
      • Stop here?

        No, that is the whole point, the user is not responsible for "stopping here." That implies that you need to get up in the middle of the night and unplug you device.
        dpatjhh
    • What? Can't you read??

      As the author pointed out, the battery charging electronics slow down the rate of charging when the battery reaches capacity. Just because the iPad 3 continues charging for an hour after it reads 100%, that doesn't mean it is adding 20% more charge. In that last hour of "silent" charging, only 3% more charge is added. Here's another way of looking at it. If you leave your iPad plugged in after it reaches 100%, the electronics slowly top it off to 103% to give you a little extra boost. Mmmkay?
      pjs_boston
      • Are you sure about that?

        The man who discovered it claimed 20% more charge, not me.
        slickjim
      • @Peter Perry

        Please point me to that 20% claim.
        msalzberg
      • The rating system is so funny

        The above post squashed Perry's post (pointing out he just needed to read the article), the MS fanboys start rally around rating it down. Fun to watch:-)
        Richard Flude
    • Where do you see...

      the figure "20%" reported.

      Maybe it's me, but I haven't seen that number anywhere but in your posts.
      msalzberg
    • Nothing like exaggerating the argument

      It's gone from 5% to 10% to you now saying 20%. What is the real issue, if any?
      Vulpinemac
      • A little off the mark, but here's the scoop.

        No one seems to know what "fully charged" means and why there's an algorithm in there beyond "guessing" the total charge on the battery. This is a mistaken impression. The algorithms have nothing to do with the 100% mark on the charge. Rather they are trying to estimate the 0% mark beyond which the battery will also be damaged and become unable to be charged at all. Only the old fashioned "dumb" chargers of pre Lithium Ion battery technology (so called "trickle charge" types can cause the "exploding battery" problem and LiIon batteries aren't so handicapped. Proper charging of any secondary battery technology uses two temperature sensors and current/voltage monitors to tell when the battery is fully charged. You will note that modern LiIon battery packs all have three terminals. An embedded temp sensor and a bit of flash are on that third wire (the flash holds the charge/discharge history of the battery). The charging cycle to 100% of battery capacity is easily told by these sensors as well as prevention of severe overheating during the charge cycke as well as discharge. Failure of this on some poorly made battery packs has caused laptop fires and virtually all other LiIon battery fires over the years. I exclude the shorting of unprotected batteries or physical damage to a battery pack here.

        Dr. Soniera is right, the 100% gaffe is an oversight, not a "safety margin"... someone got the calibration of the sensing circuits, purely a software issue, slighly off.

        I know this having done the same for Sealed Lead/Calcium and Lithion Ion battery charging systems I design into my equipment. Engineering can be a bitch and the poor guy that made this goof is probably gonna have a sore arse for a while :P
        RyuDarragh
  • Mostly about the scale of the meter

    Of course you *could* do some math and make the meter linear even if the battery's voltage relative to its charge is not linear. Last I checked, most mathematical functions have an inverse.
    CobraA1
  • What?

    The facts are clear yet we must be too stupid to see them. The Ipad 3 or new Ipad has a few design flaws. Period. Get over it I am sure a software update will fix the flaws. Next time it might be prudent to properly review a product before you declare it a must have and perfect.
    adholt
    • Who did that?

      adholt
      Seems these so called issues fall under the "minor" category. Some will fade without any intervention on Apple's part others like you said might require a smallish software tweak. Mountain meet Mole Hill. Mole Hill.... Mountain.

      Pagan jim

      Pagan jim
      anonymous
    • That is exactly the point!

      This is a very small issue and if anything it benefits the customers...

      So, why proclaim that the whole thing isn't real? Why post an article claiming 100% is actually 80% as though Apple expects you to sit there and watch the battery charge and pull it off immediately when it hits 100%.

      Reality is, this is not a real big issue and is absolutely a software bug so, these Zdnet bloggers should drop the apologetics and let it go because, they are making it worse.
      slickjim
      • Well there is the other side... After all it was called "Batterygate"

        Before this article came out:). Did you go to those to point out the silly?

        Pagan jim
        anonymous