We've talked about Mophie's Juice Pack rechargeable external battery cases for iPhone before; we did a review of an early model and have given you the news of the Juice Pack Plus for iPhone 4. We finally got our hands on a Juice Pack Air for iPhone 4 for review purposes, so now it's time to give you the skinny on how this battery pack works with the latest incarnation of the iPhone.
Design and size
Like the previous version for earlier iPhones, the Juice Pack Air for iPhone 4 comes with a USB-to-micro USB cable that is used for syncing and charging the case. The four LEDs that are used to indicate the amount of charge in the battery pack are still there, but have moved to the bottom of the case from the back -- I'm speculating that this was done to make the case thinner.
The older Juice Pack seemed somewhat flimsy to me, but the iPhone 4 edition seems to have been designed with more strength in mind. The case has a silver-colored band around the side to mimic the iPhone 4's stainless steel antenna, and comes in either black, red or white plastic. Installing the case is a cinch: you slide off the top of the case, slide in the iPhone 4 dock connector first, and then slide the top of the case onto the top of the iPhone. The weight of my "naked" iPhone 4 is 4.9 ounces (139 grams); the Juice Pack Air brought the total weight up to 7.3 ounces (207 grams). Without the Juice Pack Air, your iPhone 4's dimensions are 4.5 x 2.31 x .37 inches (115.2 x 58.6 x 9.3 mm); with the battery case installed, the dimensions swell slightly to 5.07 x 2.51 x .68 inches (128.8 x 63.8 x 17.3 mm). There's a photo of the phone and case side-by-side on the next page.