Mophie Juice Pack Air for iPhone 3G review: Mophie Juice Pack Air for iPhone 3G

Editors' note: We updated this review on April 21, 2009, to correct an error. The Juice Pack uses a Micro-USB cable instead of a proprietary cable.

Considering the iPhone 3G's short battery life, an extended battery should be the first accessory you buy. The $80 Juice Pack Air is the newest of this sort of accessory, and it is the thinner, lighter version of Mophie's $100 Juice Pack. The Juice Packs are cases for the iPhone 3G that also act as extra battery packs, thanks to their included lithium polymer batteries.

The Juice Pack Air looks identical to the original Juice Pack, with one addition: the top portion of the phone is now covered, giving the iPhone complete protection. The "air" in the name refers to Mophie's contention that the new case is thinner; however, with dimensions of 4.9 inches tall by 2.59 inches wide by 0.75 inch thick, the new case is not much smaller than the original. Also, it adds about 20 percent more weight to the phone, which is slightly lighter than the original Juice Pack. Aesthetically, the new Juice Pack is a better-looking case than the original version.

The "Air" in the name also indicates that you won't get as many hours of battery life from this case as you would from the slightly bulkier original.

The Juice Pack Air has a rechargeable 1200mAh battery, is made from matte plastic with a sleek surface that is prone to retain fingerprints, and it comes in three colors: black, gray, and violet. The accessory is divided into top and bottom sections that, when enclosed around the phone, form a perfectly snug hold that can quickly be taken apart if need be.

On the back, the Juice Pack Air has four blue LEDs that indicate the level of power left in the battery. In our experience, these lights weren't accurate; we were able to charge the phone even when the lights indicated it didn't need any more juice. On its bottom are a USB port and an on/off switch, which gives you the option to connect or disconnect the phone from the extended battery's power. The iPhone 3G charges its internal battery using power from the Juice Pack Air. When plugged into a computer, the phone is charged regardless of whether the Juice Pack Air is on.

Using the included cable, you can connect the Juice Pack Air to a computer through its USB port, letting you charge the case and sync the iPhone simultaneously--negating the necessity of the iPhone's USB cable. In our tests, it took about 2.5 hours to charge both the pack and the iPhone when starting with both completely dead.

Unfortunately, the case comes with only one Micro-USB cable, and the Juice Pack air is not compatible with a Mini-USB port. If you're planning to charge the case at two locations, such as at home and work, you'll have to bring the cable with you, unless you've purchased an extra one. It would be more convenient if the case used the Mini-USB port that's used in most handheld devices, including the original Juice Pack.

Just as Mophie claimed, using the Juice Pack Air, we got about twice the use time on our iPhone as we normally get; but, that's about half what the original Juice Pack offers. Considering that the Air is only slightly thinner than the original, we were surprised their battery lives were not more even.

Still, running Wi-Fi, GPS, and 3G on the iPhone 3G with the Juice Pack Air attached will yield about two full days of power with heavy usage.