Taken from : http://www.macnn.com/reviews/mophie-juice-pack-air-for-ipod-touch-4g.html
Mophie juice pack air for iPod touch (4G)
May 28th, 2011Mophie brings its battery tech to the fourth-generation iPod touch.
Its cases having long been a staple of the iPhone world, Mophie's latest product is only the company's second attempt at a battery case for the iPod touch. Is the accessory an essential add-on, or more trouble than it's worth?
For all of Apple's bragging about battery life, it's a fact that the company's handhelds don't always last as long as they should. An international flight or even a long workday can be enough to finish a battery off. Most complaints, though, are directed at the iPhone, which is constantly chewing through power thanks to different combinations of Wi-Fi, 3G and GPS, not to mention apps. iPods are relatively immune to drain -- the Touch is the worst of the bunch just because it behaves most like an iPhone.
Enter Mophie. The accessory maker is, of course, best known for its Juice Pack battery cases, and today we're looking at the latest model, the Juice Pack Air for the fourth-gen iPod touch. The tests the case must pass are relatively basic: how much power does it supply? How well does it protect an iPod? And is it convenient to use, as any good accessory should be?
Assuming the case has zero charge, it takes about two hours to completely fill its 1,000mAh battery through a bundled micro USB cable. For this reason among others, it's usually a bad idea to let an Air drain completely; part of the point of the device, after all, is to have emergency power when you need it. An important feature is a small switch that turns the case on and off, allowing you to rely on a Touch's internal power until backup is critical. More on this later.
Slipping the case on is easy enough. It uses a sled design, so the only trick is lining an iPod up with the grooves and pressing it in deep enough to guarantee a link with the 30-pin connector. Once everything is secure, all you need to do is slide the endpiece on and you're set.
Once the case is together, perhaps the most immediate sensation you'll get is solidity. An iPod suddenly feels like a unit, for lack of a better term -- whereas Apple is obsessed with beauty and the thinnest possible shape, often to the detriment of practicality, the Air's relative bulk makes it more comfortable to hold and gives the impression that scratching or dropping a Touch is no longer a worry. If only iPods came like this out of the box.
The only unprotected part of a Touch becomes the touchscreen. Although the Air adds a slight lip around the display, allowing an iPod to be placed face-down, it probably won't be enough to save a player should it land hard facing the wrong direction. Mophie should should keep this in mind for future designs, since the Air is otherwise extremely rugged.
Consider its ports. While the speaker and the headphone jack have some unnecessarily exposed metal around them, the rims of the case are thick and deep enough that there's not much to worry about. The Air also avoids the cardinal sin of using one gaping hole for the base; instead, the middle section of the case wraps around the dock connector. One of my favorite design aspects is the button overlays, which not only protect the volume and sleep buttons but have the same instant response as a naked iPod, unlike some silicone cases.
At 1,000mAh the Air is certainly a bit light on juice next to other battery cases, but for what it is it I doubt anyone will be disappointed. Mophie claims that the case will “virtually double” a Touch's battery life, adding an extra 34 hours of audio, or 6 hours of video. On its own a Touch should be capable of 40 hours of audio and 7 hours of video, in theory giving combined totals of 74 and 13 hours, respectively.
Leaving an iPod running for over three days straight is a tad impractical under review deadlines, but one thing that was accomplished was a stress test. A partially depleted Touch was allowed to go totally dry overnight, and then charge in the morning by turning on the Air. After a couple of minutes of unresponsiveness the iPod rebooted, then started operating normally while its power refilled. Over 10 hours later, the Touch still indicated three-quarters charge after some light use. Needless to say, the Air could be a lifesaver if you absolutely need to have access to an iPod but expect to be away from a USB port.
Here's where the Air begins to falter. On one level it makes carrying a Touch around a joy, since it improves grip and can slip in and out of a pocket without worries about scratching or recharging. There is however a serious and potentially fatal flaw: trying to remove the iPod. The case puts up so much resistance that the feat is, without exaggeration, nigh-on impossible, and indeed the first night I tried to take it off I had to give up the struggle until the next day. You'll want to avoid removing the case in all but the most critical circumstances.
This wouldn't be as much of an issue if it weren't for the Air's handling of USB. Only micro USB can be used for charging and sync, since the Touch's own 30-pin connector is completely blocked off and no duplicate is provided. That means that when the case is on, a Touch can't be docked with any other iPod-certified gear, such as speakers or FM transmitters. A trait that might only be a minor drawback for an iPhone can be a deal-killer in this scenario, since apps aside, the whole purpose of the Touch is music and podcasts.
A minor quibble by comparison is that the case doesn't function properly when using a USB extension cable. Trying to sync with one in place produced multiple error messages in iTunes, even one suggesting that the Touch needed to be restored. Mysteriously, everything returned to normal with a direct connection.
I want to love the Juice Pack Air more than I actually do, sadly. It feels like such a natural complement to a Touch that it could almost become a standard accessory -- something you'd buy during the same shopping trip. As things are, though, I can only recommend the case to people who can afford to leave it on permanently. There are easier alternatives for charging, including some from Mophie, and if protection is your main goal you might as well try cheaper cases like the OtterBox Commuter or the SwitchEasy RebelTouch. With any luck Mophie will loosen the deathgrip of its fifth-gen case, or at least find some way of making it dockable. They'll have an instant customer.
Almost doubles an iPod's battery life
Excellent button overlays Cons
iPod nearly impossible to remove once plugged in
Does not work with USB extension cables
Leaves touchscreen relatively vulnerable