There is a very simple logic to understanding battery options for iPhones and iPods: you can now choose from three broad categories of batteries, each offered by multiple companies, and differing chiefly in pricing, physical styling, and capacity. There are backpacks and semi-cases, exemplified by FastMac’s TruePower iV and Incase’s Power Slider, snap-on battery wands such as the Dexim/RichardSolo 1800, and cabled batteries including Just Mobile’s Gum and Gum Pro. If you’re looking for the type of battery we’re most likely to recommend — one that will continue to be useful to you regardless of which iPhone or iPod you attach to it — the primary considerations are practicality and capacity for the dollar, with looks and size meriting secondary concern. But if you want a battery designed to fit only one specific iPhone or iPod model, looks and size may become equally important to the other factors.
Mophie’s Juice Pack Air ($80) is, like TruePower iV, Power Slider, and numerous other battery accessories we’ve reviewed, an iPhone backpack: made primarily from either black, white, or purple glossy plastic, it solely fits the iPhone 3G, adding a slightly more than quarter-inch lump to its rear, bringing its thickness up to 0.75”. It also adds roughly 0.375” of height and roughly 0.15” of width to the iPhone 3G, bringing its total height up to 4.9” and width to 2.59”. There are two ways to look at these dimensions: first, they make the Juice Pack a bit smaller than Incase’s Power Slider, which measures 0.86” thick by 2.6” wide by 5.1” tall—fractions of an inch larger in each dimension. Second, and critically, Mophie achieves this feat by diminishing the capacity of the rechareable Lithium Polymer battery cell that’s inside.
Almost every one of the iPhone 3G battery backpacks we’ve tested sells for $80 to $100 and offers at least 1800mAh of capacity: enough to fully recharge a completely depleted, 1150mAh iPhone 3G battery one full time with some extra juice left over.
Connected to a fully charged iPhone 3G, these 1800mAh batteries let you run from morning until nightfall if you normally would run out of juice by the afternoon, giving travelers a way to watch a couple of movies on an airplane without worrying that they’ll have no power left by the end of the flight. Some batteries, such as TruePower iV, offer a lot more power—3300mAh—for similar prices, while Incase’s Power Slider was an exception to this rule, with only 1330mAh of power—basically just enough for a full recharge, or a doubling of the 3G’s standard run time.
Juice Pack Air goes a step further: with only 1200mAh of power, it loses a full third of the capacity from Mophie’s prior Juice Pack for iPhone 3G, falling shy of the ability to fully recharge a completely drained 3G due to energy lost during the transferring process, but coming close enough that some users won’t mind. Battery strength is indicated by four blue power LEDs and a battery level button on the back, and a power switch is on the bottom. Turned off, Juice Pack Air serves as little more than a thick case, offering top, side, bottom, and back coverage, though nothing for the 3G’s screen, camera, or buttons. A headphone port hole at the top is too small for oversized headphone plugs, but fine for others; it’s cut mostly to accommodate Apple’s and similarly thin connectors.
Should it not fit your favorite headphones, you can slip off the top of the case and expose the top portion of the iPhone 3G, cutting the protection to roughly the same degree as the earlier Juice Pack and similar competitors such as MiLi’s Power Pack for iPhone. This is a fair enough way to accommodate different headphone users, though ideally Mophie would have instead incorporated some of the smarter integrated button, film-based screen, and tapered headphone port protectors found in better iPhone 3G cases.
One certainly positive element of Juice Pack Air’s performance was its impact on the iPhone 3G’s speakerphone: there’s virtually none. Callers reported a very mild increase in sibilance when we spoke at certain volumes, as well as an extremely mild echo in their own voices that was neither consistent nor problematic. In other words, the iPhone can still function well as a speakerphone while it’s inside this accessory, which wasn’t the case with Incase’s Power Slider. We saw a little evidence of modest signal strength falloff under certain conditions, such that users can expect roughly half a bar to drop, at most. Generally, a five-bar signal stayed at five or fell to four, and the same thing happened with a four-bar signal staying constant or falling to three.
It’s also worth a brief note that Mophie’s approach to charging its Juice Packs has changed over the past couple of years. Whereas the original Juice Packs used an Apple Dock Connector port for charging, somewhat infamously installed backwards, the iPhone 3G model switched to a more common mini-USB port, and Juice Pack Air has for whatever reason switched to a micro-USB connector that saves only a little space and requires you to use either Mophie’s included cable or a similar replacement.
