acoustics and the mini USB port

Although it looks on the surface as though it should block out sound, the Juice Pack is surprisingly loud. Very subtle scoops on the front channel both the microphone and speaker sound. Ringtones had the same volume as they did with a naked iPhone. Callers likewise didn't notice any conspicuous difference in voice quality.

While this absence of change is welcome, one important but equally useful change comes through the external connection: rather than simply put an Apple-standard Dock Connector on the outside, the company uses a mini USB jack. This does rule out using certain iPod accessories directly, but it also means that virtually any mini-to-full USB cable -- such as for a digital camera -- will work for charging and syncing. Travelers who've suddenly been at a loss for an official cable may consider this feature useful all by itself.

battery life and recharging

Of course, the central feature of the Juice Pack is the extended battery life, and it's here that it excels. We found that a moderate amount of use, including a few hours of heavier-duty tasks like Internet access, YouTube videos, 3G calls and music playback, still left the phone running entirely on the Juice Pack's built-in charge for nearly a whole day. The review unit was plugged in at 7PM on one day and didn't switch over to the iPhone's own battery until 4PM the next; as such, it's entirely possible that an average user could run an iPhone for about two days.

Time hasn't allowed for testing in harsher conditions, but we have reason to expect Mophie's claims for more non-stop use to be accurate. The company expects about 6 hours of extra 3G calling and data time as well as 8 hours of video. While there will likely be some fluctuation for those on the fringe of the network (where the radio has to boost reception power) or indulging in a heavy amount of Internet video streaming, even a conservative view would still add enough time that the most committed users could still last for a day on a charge. Those who regularly use iPhones for Internet radio or as a lifeline for work will be very happy.

The only suspicion is that standby time of 350 hours is optimistic: it's likely achievable, but certainly not with the iPhone in full 3G mode with Wi-Fi enabled.

When it comes time to recharge, the Juice Pack is fairly flexible and will charge both itself and the iPhone when plugged in. It also doesn't depend on being plugged into a main USB port and will gladly draw energy from a spare port on a keyboard or a computer display. Charging itself takes a long time, however. It took well under two hours to reach about half power, but it wasn't until closer to four that the Mophie pack said it was finished. Any buyer should be careful to keep the add-on charged if they think they may only need it in emergencies.

A back power indicator not unlike the one for Apple's own MacBook batteries lets you know how much energy the Juice Pack has of its own through a button press. It's appreciated and is also intelligent enough to show relative progress when the Juice Pack is recharging, though it's not very granular with just four lights to indicate status. However, it will flash to indicate its recharge progress, which can be helpful for those who need just a short extra charge before heading out the door.

by Jon Fingas