No matter how much battery a company can pack into a handset, a battery can still run out at an inconvenient time. That's where Mophie's new Juice Pack Air case steps in, offering a protective body in a light design, with a mix of charging power.

Mophie has been known for its several charging cases released on the market aimed at keeping the iPhone charged throughout the day. Its cases utilise a built-in battery that connects to the iPhone through the Lightning connector (or 30-pin on the older models) to provide a charge on-the-go - just like the handset is plugged into a wall. The Juice Pack Air is no different.

Here, Mophie has packed its highest capacity battery ever into its thinnest, smoothest soft-touch design. The company boasts 100 per cent more battery life when the Air's charging capabilities are flipped on behind the back of the case.

The iPhone 5 slips tightly into the case, where you're not left with any fear that it may fall out. While the focus of the Mophie is obviously its charging capabilities, it does go one step further in offering a hard protective shell that keeps the device safe. The iPhone 5's buttons are accessible, though you may want to use the adapter provided by Mophie if you want to connect your headphones.

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The case charges using a microUSB cord and the iPhone 5 can be left in while it's charging, which also charges the handset at the same time. 

Presumably, Apple's Lightning connector restrictions - that makes it difficult for third-party manufacturers to integrate the technology - kept Mophie away from using it to provide the charging here. Given how massive microUSB has become outside of the Apple ecosystem, it does work well, and you can plug it into Apple's USB wall charger.

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Keeping the user in the know about how much battery is left, a charging indicator is located on the back of the case. There are four lights that will indicate how much charge is remaining when a button to the left is pushed. To begin charging the iPhone 5 - it's not automatic - the user must turn on the switch that's located in the same area.

In our testing we found battery life on the Air to be pretty good. It offers no difference from charging from the wall or from the case in terms of speed, of course you're just limited to space. But the thing about the Juice Pack Air is the fact it can charge the iPhone 5 from dead to a full charge, which in reality should get your iPhone through more than a day, if not two. 

Given the iPhone 5 is already a long handset, the only problematic area for the Air is its length. It doesn't offer much more size to the sides, but on the bottom and top it is definitely noticeable in the pocket. But for someone who struggles with battery life and needs such a case to stay afloat through the day, we see no reason the bad would outweigh the good here.

Mophie's first iPhone 5 case, the Helium, released last month, seems to have been quickly outpaced. We noted how great the Helium was in performance, but given that the Mophie Air is thinner and offers more charge, the few extra pounds for the Air seems worth it.

Priced at $99 ($66) - $20 more than the Helium - the Air will begin shipping to customers on 22 March, in red, white and black colours. If you're constantly suffering from poor battery life, this looks to be the case for you.