I have a confession to make: I do not like external batteries for mobile devices like the iPhone. I especially dislike the case-based ones—the ones that you slide your phone into with a battery strapped to the back like a jetpack. The idea of carrying around an extra battery just for my iPhone is generally distasteful to me. I think they are unnecessary for most of everyday life, which leads to a second reason... I don't like to buy (or carry) unnecessary stuff.

Recently, however, I began to change my tune and opened myself up to the possibility that there could be a mobile battery pack for me. I was traveling frequently and kept finding my gadgets on the verge of death after a long day on the road. My criteria were that it had to be smallish and easy to throw into a bag, but not so small that it's easily lost. It couldn't be built into a case, and it had to be usable with a wide variety of devices—not just my iOS devices. It also had to cost less than $100. I began to hear good things about the Mophie JuicePack Powerstation. I eventually purchased one prior to my trip to San Francisco for WWDC 2012 so I could test it out for myself. And after having used the JuicePack to recharge my iPhone 4 and third-gen iPad over the last month or so, and I am pretty satisfied with the purchase.

What you get

The current version of the Mophie JuicePack Powerstation is essentially "just" a 4000mAh external battery. A previous version of the device only had a 2000mAh battery, which Mophie claimed would double an iPhone's battery life. The 4000mAh version is double that. The battery comes in an enclosure that supports any device that can charge over USB, so it's not limited iOS devices—you can also charge Kindles, Android devices, and any number of other accessories that can plug in over USB. The charging output of the JuicePack can go up to 2.1 amps, making it suitable for charging even the third-generation iPad (notorious for taking forever to charge on lower-output USB plugs).

The device itself charges via micro USB. You can either plug it into an existing USB wall charger (which I have plenty of, due to all the iDevices I've owned over the years) or into your computer, assuming it's a high-current port. You have to provide your own cable for whatever device you plan to charge, but that makes sense. Different devices likely need different connectors anyway. The standard 30-pin USB connector for iPods, iPhones, and iPads plugs into the JuicePack's standard USB port just fine. But you won't be able to use the standard USB port to charge the JuicePack with a male-to-male cable. Micro USB is for charging itself up, and standard USB is for charging other devices.

High-speed charging

Since the JuicePack can output a fair amount of power at once, device charging is actually quite speedy. I'm regularly able to charge my iPhone 4 from near death (around 10 percent battery) to 100 percent in roughly two hours with plenty of capacity left in the JuicePack. (There are four indicator lights to show the JuicePack's current battery status, and after charging up the iPhone once, there are still three lights left).

This means you can charge multiple smaller devices on a single battery charge, which is always good. But if you're going to be using it on something with a monster battery like the iPad, you're only going to get one charge out of it. You won't get a full charge either. Mophie makes this clear on its website, but it's worth pointing out—in my trials, the JuicePack was able to charge up my third-gen iPad by about 25 percentage points over a period of two hours while the iPad was not in use, and about 15 percentage points over an hour while I was actively using the iPad. I've been impressed by how fast the JuicePack manages to do this, but it does drain the entire battery (not to mention that it gets very hot). But assuming your iPad's battery is almost dead and you can't wait to find a wall charger, the JuicePack certainly gets the job done—and relatively quickly, at that.

Despite my apparent love for this gadget, there are some things that could be improved if Mophie wanted to really go the extra mile. Primarily, the JuicePack doesn't have pass-through charging capabilities, so you can't charge it and a device connected to it at the same time. (As someone who's obsessed with efficiency, this is somewhat of a disappointment, but it's not a dealbreaker). And it might be nice if Mophie was able to offer an even higher capacity version for iPad power users. But all things considered, I'm quite happy with the current tradeoff of capacity versus size since I mostly use it to juice up my iPhone.

Overall, the JuicePack Powerstation is a straightforward product that is simple and easy-to-use. It's also comfortably small (for how high-capacity it is, it's only 4.4 ounces and the size of a deck of cards) and doesn't look too shabby either. There are plenty of other battery packs for iDevices, of course, but many of them are lower-capacity and/or built into iPhone cases—not very good for use with a variety of devices. And even those that aren't built into cases tend to be limited. I have friends who own the kind that plug directly into your iPhone's 30-pin connector, and those come with their own set of problems (lack of wide compatibility, have to use its own proprietary chargers, more pieces to lose).

For just under $80, the JuicePack Powerstation gives me exactly what I want with minimal bells and whistles. I don't hesitate to recommend it to other people looking for a simple external battery solution for their gadgets.