There are a ton of external battery packs for iPhones and iPads. I remember the good old days when it seemed like the only packs available were little blobs that you'd plug into the bottom of an iPhone to keep it going for a few more hours. Now everybody and their brother-in-law has an external battery pack in their line, so it's nice to see one that's completely different from the rest of the pack. It's the Exogear Exovolt Plus, which has the distinction of being a stackable battery pack. Read on -- we're going to give away some goodies to one lucky TUAW reader.

Design and Functionality

The Exovolt Plus comes in two models: the main battery (US$89.95) and sub batteries (US$49.95 each). To power your iPod touch, iPhone, or iPad, you need at least one main battery. It has a micro-USB port for charging and a full-sized USB port to charge up your devices. There's also a power button and four white LEDs that give you the relative charge level of the stack of batteries.

The sub batteries are slightly thinner, don't have the ports, but do have a small socket on one top corner that contacts a male connector on the bottom of the main battery. The sub batteries also have one of those male connectors on the bottom, so you can stack as many of them as you want to to create a tower of power.

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The Exovolt units are white, about 3-3/4" square, and have rounded corners. The bottom sides are blue, and there are small latches on the sub batteries to insure a solid connection to the main battery or other sub batteries.

To make sure that your stack 'o power is safe to be around, Exogear built in double circuit protection, overheat protection, short-circuit protection, and an automatic input/output control. The main battery package comes with a carry pouch, micro-USB and Dock Connector