Starting with Mophie’s Juice Pack and continuing through Incase’s Power Slider Case, we’ve reviewed a number of different iPhone-specific battery backpacks over the past year, each with the same general concept. Rather than dangling or hard-suspending the battery from the iPhone’s bottom, these accessories thicken the iPhone somewhat by placing their rechargeable cells on the iPhone’s backs, using a Dock Connector plug and speaker/microphone pass-throughs on their bottoms. The latest such option is FastMac’s TruePower iV ($100), which was originally announced in January of this year, but has been beset by both iPhone changes and manufacturing challenges. Today’s iV is substantially the same as the one that received a “Best in Show” award back in January, but it’s also a little different.

There’s some very good news to share up front about iV’s design: it is, at least for now, the best backpack-style battery we’ve seen at this price level. In addition to including a screen protector and iPhone-friendly headphone extender cord that aren’t shown here, FastMac has packed it with both the most capacious battery in its class—a 3300mAh cell—that as explained below let us use an iPhone 3G actively and continuously for two full days while traveling.
Additionally, iV includes thoughtful features that truly distinguish it from its peers. It contains a bright LED light that can be switched on to improve the lighting of your iPhone photographs, a first in iPhone backpacks, plus a full-sized USB port that you can use with another cable to charge any other USB device.
FastMac also uses a female Dock Connector rather than a mini-USB port on the bottom, enabling you to recharge the battery using your iPod or iPhone’s included cable or virtually any Universal Dock accessory.
The only modest inconvenience of this port is that the device’s charging lights, charge indicator button, and power button are all found on its back, so you don’t know for sure that iV is charging unless you turn it or your dock-based charger around. On one occasion, we placed it on a charger and came back to find that we hadn’t seated it properly, so it hadn’t been charging; as the battery requires up to six hours to completely recharge, making sure that it’s doing what it should do is pretty important, and mounting a power lamp on the front might have helped.
Our testing results with iV were generally highly positive. Unlike the Mophie and Incase batteries, which provide barely enough juice for a full recharge of the iPhone or iPhone 3G, FastMac’s battery has enough power to recharge the iPhone fully twice, and the iPhone 3G around two and a half times. As a test to see how the battery worked, we gave iV and an iPhone 3G each a full charge prior to a two-day series of flights from Hawaii to the West Coast, and the West Coast to the East Coast, then proceeded to make calls, play games, watch movies, and use 3G Safari and e-mail features—circumstances that typically result in a full drain of the iPhone 3G’s battery within half a day. With iV attached, we made it through the full two days of travel with 10% of the iPhone 3G’s battery to spare, despite never recharging either device mid-way through the trip. There’s currently no other backpack-style solution that offers such performance for this price.
Though it is not perfectly implemented due to Apple hardware limitations, we also really appreciated iV’s inclusion of a photography-aiding light solution. Ideally, an external flash could be triggered only as necessary, but since that’s not possible, FastMac gives you a white LED with a switch to turn on and off as necessary, functioning like a bright flashlight.
The differences in the iPhone 3G’s camera performance were profound.
Images that would have been rendered pitch black suddenly became fully visible, and images that were in dicey light before, subject to motion blur, became clearer and more detailed—at a slight, but acceptable color balance cost. Contrast this useful, smart feature with the less thoughtful, throwaway inclusion of a laser pointer and LED on RichardSolo’s 1800-series battery; it’s obvious who has been thinking of real solutions to problems using the same components.
Most of iV’s issues are small ones. The power button on the back, appropriately touted as a means to let you regulate when you want to activate the battery for additional power—or deactivate it to conserve the cell—is too easy to depress accidentally when the phone’s coming in or out of your pocket, and could benefit from a subtle redesign. FastMac’s audio pass-throughs for the speaker and microphone work very well when you’re talking on the iPhone as a handset, but not in speakerphone mode, where the speaker creates objectionable feedback—a problem we also saw in Power Slider. One omission from the original iV’s design is a hybrid belt clip and video stand, a feature we liked, but also thought was overly bulky; for better or worse, this feature is no longer part of iV.
And then there’s the accessory’s size; FastMac has sculpted a rubber-coated black plastic frame that is now able to fit both iPhones and iPhone 3Gs, as well as guaranteeing iPod touch and iPod nano charging compatibility. This is no easy feat; Incase and Mophie both expect you to buy multiple batteries for multiple devices, and in fact, FastMac’s original incarnations of iV did the same, which is less than ideal for any battery, let alone a $100 one.