Taken from : http://www.macnn.com/reviews/mophie-juice-pack-air.html
mophie Juice Pack Air
May 30th, 2009A slimmer iPhone battery that trades longevity for portability.
Battery packs for iPhones often dramatically extend the useful lifetime of Apple's devices, but they also add considerable bulk and rarely feel like natural extensions of the iPhone itself. Mophie wants to change this with the Juice Pack Air; we'll see not only whether it accomplishes its intended goals but whether it or the original Juice Pack is the better choice.
design and hand feel
The core battery section of the Juice Pack Air is, from a basic perspective, very familiar to anyone who's used the regular Juice Pack for the iPhone 3G. It almost entirely envelops the bottom two thirds of the phone, excepting the screen. A pair of scooped-out sections near where the iPhone's Dock Connector plugs in ensure that calls and audio aren't muffled by the case; we didn't have any problems with audio in testing.
As the MacBook Air-inspired name suggests, it's decidedly thinner than the earlier model. Where the original at least doubles the iPhone's effective thickness in your pocket, the Juice Pack Air only extends that by just over half of the iPhone's original thickness. In the pocket, it's noticeable -- though we'd say it's still comparatively thick. This isn't for owners with tight pockets.
Almost more significant than the thickness, though, is the top shell. The Air adds a second piece that offers very nearly complete protection of the rest of the iPhone's back; the only exposed areas are those needed for the buttons, camera lens and headphone port. It's a very welcome addition and may be worth the sacrifice for those truly worried about scratching or dropping the iPhone the wrong way. Pressing the buttons is made slightly more difficult, but not so much as to be inconvenient. The only true complaint is that it's particularly difficult to remove once it's attached, but it's thankfully optional.
Other features are again very much familiar, but with an important twist. You still have a USB port to sync with a computer while charging the case, and a four-light, button-activated battery gauge. However, it now uses what appears to be micro USB instead of mini USB and is therefore more dependent on keeping the proprietary cable. Thankfully, there's now also a switch to toggle whether power flows from the pack to the iPhone. It's an extremely handy option to prevent the Air from recharging the handset when you don't need it -- such as when you're about to return home to a charger -- or simply to run on the iPhone's own battery first. It's not a factor very often but is appreciated.
One key change from the standard Juice Pack is decidedly worse, though: the texture. The full-size model has a rubberized grip that renders it much easier to hold, but the Juice Pack Air has a glossy, smooth plastic finish much like the iPhone 3G itself. Grip as a consequence is no easier. Outside of it fitting more snugly in the hand due to girth, the Air still triggers worries that it might slip out of your hand in too-casual handling. We'd be willing to pay extra just for the better surface, and the full Juice Pack's extra battery capacity makes that leap all the more tempting.
battery life and recharging
While the tendency is towards battery life über alles in most iPhone battery packs, mophie has consciously avoided this with the Air and readily admits as much: it's a hard shell case that just happens to have enough extra battery to keep a handset running longer each day.
With this in mind, the Air is still somewhat disappointing. From a full charge, the slim Juice Pack gave out in about three hours after a mixture of 3G and Wi-Fi browsing, music and short phone calls. Even though most of this was demanding, the test fell significantly short of mophie's claimed 4.5 extra hours of pure 3G browsing, let alone the extra time afforded by calls and Wi-Fi data. We hope this was more an exception than the rule, but as-is won't compare well to the full Juice Pack's ability to run for several hours at a time and effectively granting an extra day of battery life for moderate iPhone users.
Filling the Juice Pack Air back up takes roughly the same time: that is, it's typical but slow. The halfway point arrives quickly when charging the case alone through a computer's powered USB port, but as with most lithium-ion batteries, the rate of charge quickly slows down the closer you approach a full charge. It took a total of just over four hours to have a complete battery. Frequent flyers and others who need a constant charge should definitely consider toting either their notebooks or their iPhone AC adapters and prepare to start recharging immediately whenever the battery is either low or drained out; it won't be possible to get a practical emergency charge.
It may sound like we dislike the Juice Pack Air, but that's not the case; the top protection, slimmer profile and price could make it a great fit for anyone who wants both casing and battery but something that can still fit in a (reasonably sized) pocket. We wish it had a screen protector, but few guards outside of flip cases and sleeves truly offer enough front protection regardless, and not everyone likes those form factors. Compared to other competitors, this newest entry does an excellent job of preserving audio quality.
The real concern is the sheer number of qualifiers attached to recommending the Air over its thicker sibling. As of this writing, there's only a $20 gap between the two mophie cases; given that the Air itself starts at $80, it's not hard to quickly rationalize jumping to the regular Juice Pack for the greatly improved battery life or the easier-to-hold surface. The latter's use of mini USB also simplifies recharging: any A-to-B USB cable from a camera or printer will do, while the Air's micro USB isn't proprietary but also isn't as ubiquitous, either.
Whether you enjoy the Air consequently hinges on just how you use it. If it's simply to provide enough extra time for calls or Internet access after the workday is over, the smaller design works beautifully and saves some money in the bargain. But if you're the sort who regularly spends hours at the airport waiting for connecting flights or use your iPhone so often that it often needs a recharge in mid-day, the $100 model is undoubtedly the better option.
- Slimmer, more totable design.
- Top protection finally arrives.
- Audio quality preserved with the case on.
- Much less extra battery life than the full model.
- Surface is just as slippery as for the iPhone 3G.
- Micro USB somewhat less common for charging.