Once you've bought an iPhone 3G, attempting to extend its short battery life may be high on your list of priorities. Available for around £65, the mophie Juice Pack Air is the thinner, lighter version of mophie's £80 Juice Pack. The Juice Pack Air is a protective case for the iPhone 3G that acts as extra battery pack, thanks to its included lithium-polymer batteries.
Design-wise, the Juice Pack Air is similar to the original Juice Pack, with one addition: the top portion of the phone is now covered, giving the iPhone complete protection. The 'air' part of the name refers to mophie's contention that the new case is thinner and lighter than the old one. At 75g, compared to 85g, the new case is lighter, but, measuring 66 by 124 by 19mm, it isn't much smaller than the original. Aesthetically, it's an improvement though. The Juice Pack Air increases the iPhone's weight by about 20 per cent.
The Juice Pack Air has a rechargeable 1,200mAh battery, is made from matte plastic with a sleek, fingerprint-prone surface, and comes in three colours: black, white and purple. It's divided into top and bottom sections that provide a perfectly snug hold when enclosing the phone.
On the back, the Juice Pack Air has four blue LED lights that indicate the level of power left in the battery. In our experience, these lights aren't accurate -- we were able to charge the phone even when the lights indicated it didn't need any more juice. On the Juice Pack Air's 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 battery 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, and rendering the iPhone's USB cable unnecessary. 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 isn't compatible with mini-USB cables. 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, although they're not as easy to find as a mini-USB cable. It would be more convenient if the case used a mini-USB port, like most handheld devices, including the original Juice Pack.
In line with mophie's claims, when we used the Juice Pack Air, we were able to use our iPhone for about twice as long as normal. But that's about half what the original Juice Pack offers. Considering that the Juice Pack Air is only slightly thinner than the original, we were surprised that their battery lives aren't more similar.
Still, running Wi-Fi, GPS and 3G on the iPhone 3G with the Juice Pack Air attached will yield about two full days of heavy use.
The mophie Juice Pack Air is an easy way to protect and extend the battery life of your iPhone 3G. But the fact that you have to use a micro-USB cable is disappointing and we'd expect to get more battery life out of the device, given its size.
Edited by Charles Kloet