Battery Life

For a company that has been so laser focused on reducing weight and device thickness, the new iPad actually growing in both of these dimensions was unexpected. From a technical standpoint, the tradeoff makes sense. The new Retina Display consumes significantly more power than its predecessor, as do the A5X and MDM9600 baseband. Both of those ASICs are still built on a 4x-nm LP process and will surely increase power consumption over the iPad 2.

With more transistors switching on the same process node and a display (and backlight) driving more pixels at the same brightness, the battery either had to be larger or battery life would suffer. Apple understandably chose the former and the new iPad ships with a 42.5Wh battery—the largest we've ever seen used in an ARM tablet. The new iPad's battery is so large it's even bigger than what Apple uses in the 11-inch MacBook Air, and it's within striking distance of the 50Wh unit you'll find in the 13-inch model. I do believe this move says a lot about how Apple sees the iPad moving up in the world, but I'll get to a discussion about that later.

With a 70% larger battery than the iPad 2 but with more power hungry components inside, how does the new iPad fare in real world usage? Subjectively: it doesn't last as long as its predecessor. Objectively, our numbers seem to agree.

Our web browsing battery life test browses through dozens of web pages, pausing on each to simulate reading time, until the battery is depleted. All of our tests are run at the same brightness settings (200 nits) to ensure we are comparing apples to apples.

Web Browsing Battery Life

On WiFi we measured an 8% decrease in battery life compared to the iPad 2—nothing huge but not insignificant either. Fall off of WiFi and depend on LTE and you'll see around a 9% decrease in battery life, again—noticeable but not unusable.

I also threw in numbers from the Motorola Xyboard 10.1, an LTE enabled Android tablet running 3.2. Equipped with a much smaller battery (~26Wh), the Xyboard 10.1 delivered 7.31 hours in our LTE web browsing test. The new iPad managed to last 16% longer on a single charge—a smaller advantage than you'd expect given the 70% increase in battery capacity, showing just how much power the new Retina Display and its backlight consume.

The iPad is more than usable on long flights or throughout the day without being tethered to a wall outlet, but in practice you can expect a decrease in battery life compared to last year's model.

Keep in mind that these values are all at 200 nits (roughly 70% brightness on the iPad). If you use the iPad at max brightness (~400 nits) you'll see considerably lower numbers:

Web Browsing Battery Life

In our web browsing test, at max brightness, we saw 5 hours and 34 minutes of continuous use before the battery died. The iPad 2 incurs a similar penalty, lasting under 7 hours in the same test. Do keep this in mind if you need to get a lot of untethered use out of the new iPad. In order to come close to Apple's battery life estimates you'll have to be below 70% brightness.

Charging

Despite the significant increase in battery capacity, Apple continues to ship the new iPad with the same 10W USB power adapter as the previous two models. You can charge the iPad via a Mac/PC USB port that implements the USB charging spec, however doing so will take a minor eternity to fully charge the tablet. Just as before, the new iPad will not charge off of a USB port if the tablet is awake; it will only charge when locked/asleep. The convenience of having a USB based charger is evident, but you'll want to stick with the 10W adapter to actually charge the iPad.

Charging the larger battery does take longer. If we measure from a completely dead state to when the iPad indicates that it's fully charged the increase in time is approximately 50%, from 4 hours with the iPad 2 to 6 hours with the new iPad. ASUS' Transformer Prime, by comparison, requires only 2.5 hours as it ships with an 18W charger. And no, you can't use ASUS' charger to speed up charge times on the new iPad—when connected, the TF Prime charger will only supply 9W to the iPad.

Charge Time

The story doesn't end there however. While the iPad 2 will draw 0W after its 4 hour charge cycle is complete, the new iPad will continue to draw around 3W after it claims to be fully charged. This will continue for roughly another hour at which point the power adapter will draw anywhere from 0.1—0.6W.

Note that when running at full brightness and with a heavy GPU load (e.g. Infinity Blade 2), the power adapter can't supply enough to keep the iPad charged and drive the display/internal components. 

There's no good solution here other than for Apple to start shipping the iPad with a higher wattage power adapter. I do believe faster charge times are going to be necessary if Apple is keen on sticking with this larger battery, not to mention the usage issues of not being able to maintain charge equilibrium under load.

Thermals

The increase in power consumption of the new iPad also manifests in the form of increased heat production. A 163mm^2 SoC built on a 45nm LP process is a serious chip. Although it doesn't run hot enough to require active cooling, the SoC alone is responsible for a couple of watts of the iPad's TDP under heavy load. Combine that with a 45nm LTE modem and the heat put off by the more powerful backlight and you've got a recipe for a noticeably warmer device.

Does the new iPad get warmer than the previous one? Absolutely. I would even go as far as to say that it can get uncomfortably warm, but it never gets too hot to hold. If you've used any of the modern Mac notebooks, I don't believe it's anywhere near as bad.

When holding the new iPad in portrait mode, with the home button at the bottom, the lower left corner of the device ends up being the warmest. Along the left edge of the iPad is where the logic board resides, and the lower half is home to the A5X SoC. Under load, particularly a heavy GPU load (e.g. playing a 3D game), this area is going to heat up quickly.

I took several measurements using a contactless IR thermometer in the same ambient conditions on a new iPad vs. the iPad 2. The results are below:

Thermal Comparison (Max Temperature)
  iPad 2 iPad (3rd generation)
Web Browsing (2 hours) 32.7˚C 37.6˚C
Infinity Blade 2 (1 hour) 34.2˚C 41.9˚C

Again, I don't believe this is a deal breaker but it's the obvious result of remaining on Samsung's 45nm LP process combined with a more power hungry display/backlight. I suspect there will be improvements in efficiency on the display side over time, but I can't see the Retina Display being any lower power than the iPad 2's 1024 x 768 screen. The real avenue for improvement will be when Apple shifts to 28/32nm silicon for the SoC and LTE modem. If you want a cooler running iPad, you'll have to wait until next year for that.

Handheld Image Editing: iPhoto for iOS The A5X SoC
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  • zanon - Wednesday, March 28, 2012 - link

    In the article:
    Alternatively, we're used to a higher resolution enabling us to see more on a screen at one time. In the case of the new iPad, the higher resolution just makes things look sharper.

    The higher resolution does make smaller fonts readable. For something like an SSH session, that really will mean significantly more stuff can be on a screen at once.
    Reply
  • MobiusStrip - Thursday, March 29, 2012 - link

    A more useful change would be abandoning the ridiculous glossy screens. It's sad that Apple takes its cues from the plastic schlock being peddled at Best Buy, and participates in this fraud of shoving glossy screens down customers' throats. Reply
  • repoman27 - Thursday, March 29, 2012 - link

    The plastic schlock at Best Buy has a glossy plastic film applied to a cheap TN panel. Apple puts a piece of glass in front of their much more expensive IPS panels to protect them. The only way to make that glass (or the glass of the LCD panel itself) matte would be to apply an antiglare plastic film coating to the glass. These films have drawbacks (they block and scatter light making small details and text blurry.) The drawbacks become more exaggerated the farther the front surface of the glass is from the plane of the actual LCD.

    But you're right, it's probably Apple copying the design language of sub $500 laptops in order to somehow defraud the general public and force their customers to buy the products they actually produce.

    And seeing as how this discussion is about the new iPad screen, I'd like to point out that you're complaining about the lack of an antiglare coating on a touchscreen device... Strong work.
    Reply
  • Sabresiberian - Thursday, March 29, 2012 - link

    How is it fraud? Apple isn't, like, saying their screens are anti-reflective and then giving you totally reflective glossy screens.

    Many people prefer a glossy screen and simply aren't bothered by background reflections.

    ;)
    Reply
  • Henk Poley - Monday, April 2, 2012 - link

    Yes, Apple really should use Schott Conturan/Amiran/Mirogard antireflective technology.

    btw, not-glossy does not mean matte. Air is not matte either. Glass can be see-through too ;)
    Reply
  • Watwatwat - Monday, April 2, 2012 - link

    Nope, steve gibson has tested even using screen protectors on the new ipad vs not, it seems to affect the resolution at that level, matte might not be a good idea at all for high density display. Reply
  • KoolAidMan1 - Thursday, March 29, 2012 - link

    I wasn't initially blown away, but then after a day of using it every other display seemed bad in comparison. It is one of those things you didn't realize was needed until using it, now I want very high DPI in all of my monitors. Reply
  • menting - Wednesday, March 28, 2012 - link

    Is it just me, or do Shadowgun and GTA screenshots look more detailed in Transformer Prime than in the iPad? Reply
  • menting - Wednesday, March 28, 2012 - link

    nm..i just noticed that it's scaled up in new ipad, so it's definitely not as sharp.
    However, how can fps be fairly compared in this case then?
    Reply
  • TheJian - Wednesday, March 28, 2012 - link

    Basically because of the way Nvidia and Apple approach games so far, you can expect games on Tegra3 to just look better as they seem to aim for more graphics and fewer games (they spend money on fewer projects that produce better results), as opposed to apple who spreads the wealth but just ends up with more cannon fodder if you ask me :) You should get more variety on Apple I'd guess, but a better experience with fewer choices on Tegra3/Android. I like QUALITY over QUANTITY personally and hope Apple leans the way of Nvidia in the future. I would rather have 10 games that I'd play for weeks or months (if I'm playing on my hdtv through one of these I want better water, buildings etc) rather than games I fire up for less than 20 minutes as their just another angry birds variant and arguably useless on your TV.

    I want these devices to KILL the consoles next year and make MS/Nintendo etc give it up in 2015 or whenever the next revs should come. I hope they just realize we won't buy them anymore. DirectX11 on my phone/tablet and probably standard 25x14 resolutions by then (won't all be retina by 2015?) make a console purchase STUPID. This could be the merging of console/pc we need since phones/tablets rev yearly like pc's instead of 10yr console's stuck in stone stagnating gaming. Your phone as a portable console with xbox/ps3/pc gamepad support would be excellent. Pump it out to a monitor and keyboard/mouse setup and you have a notebook replacement too...LOL Now if they'd just put in a few extra cores by then that will disable if on their own screen but turn on when on a larger display like TV/Monitor and we have exactly what we want in both cases :)

    Pipe dreams? Retina is here now, and gamepads sort of. Next stop cores that only turn on depending on display output :) Awesome battery on the road, and great power in the dock at home pushing your 27in monitor. :) The 28nm versions by xmas of everyone's chips should come close to console power or surpass them. Interesting times.
    Reply

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