It seems like Google Glass has the same Achilles heel as most mobile devices: a short battery life. And so, even if the device isn’t for sale yet, someone’s already come up with a complementary external battery pack for it. It’s called PWRglass, a 1400mAh battery pack that looks like a lanyard.

The company behind PWRglass claims that the battery is equivalent to almost three times the unspecified battery life of Glass. While Google claims that the device’s built-in battery is enough for “one day of typical use”, PWRglass explains that it will only last 51 minutes of continuous video. That’s one of the most popular applications of Glass to date. With PWRglass, you can continuously shoot with Glass for up to 2 hours and 21 minutes. The video below – showing the PWRglass crew getting a second Google Glass test unit – proves that claim:

Because Glass uses a microUSB charger, I bet it will work with many external battery packs, but the PWRglass does make it easier to carry that extra power around.

[PWRglass via Gear Diary]