On the case
The base of the Juice Pack Air is very similar to that of the Helium: The Micro-USB port at the bottom (which can charge both the case and an iPhone 5 inside the case) is surrounded by a metal plate, suggesting that perhaps one day Mophie might release a contact charger for its cases. And as with the Helium, the Air's design leaves your iPhone's headphone jack deeply recessed--while thin plugs like the one on Apple's stock EarPods will fit through the case's opening, the larger plugs on some third-party headphones will require the use of the included adapter.
On the back of the base sits a button, four LEDs, and a switch. Press the button, and the LEDs light up to indicate how full the battery is. The case powers your iPhone only when you flip the switch to on. Mophie recommends turning on the case only after your iPhone's built-in battery drops below 20 percent. To maximize battery life even more, the company suggests turning the case off again once your iPhone passes the 80 percent charged mark again. (The company says that charging the final 20 percent of the iPhone's battery requires more power than increasing the phone's battery by 20 percent at lower starting levels.)
Where the Juice Pack Air differs notably from the Helium is with the way it deals with the iPhone's side-mounted controls. While the Helium (like the Juice Pack Air for the iPhone 4 and 4S) uses cutouts around the iPhone's buttons and controls, the new Juice Pack Air (like the old Juice Pack Plus) instead employs button overlays: Tiny buttons built into the case cover the volume and Sleep/Wake buttons, and a pass-through switch activates the phone's Ring/Silent switch. I prefer this approach, as I find the Helium's cutouts make using the controls a bit of a hassle.
The buttons on the Juice Pack Air aren't as responsive as the ones on the iPhone itself, or even as the ones on the Juice Pack Plus. The volume buttons in particular just don't have a lot of motion to them, so though they're easy to press, you don't get much tactile feedback. Still, as I said, I prefer these buttons to cutouts, and I'm glad they're there.
Like the Helium, the Juice Pack Air charges at 1A, where previous Mophie cases charged at 0.5A instead. The result is that your iPhone 5 charges fairly quickly, but the case also gets noticeably warm around the bottom during the process. You're not going to get burned while an Air-clad iPhone is in your pocket, but you'll feel the heat.
In my review of the Juice Pack Helium last week--yes, last week, Mophie--I wrote that I didn't love the headphone-jack situation, and that while I liked the case, I wished it had button overlays and provided more power. I concluded, "I'm still holding out hope for a Juice Pack Plus II." I didn't know the wait would be so short: That's essentially what the new Juice Pack Air is. It doesn't fix the annoying headphone-jack issue, but the Juice Pack Air case doubles your iPhone 5's battery life, fits well, looks good, and is a pleasure to use.
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