Mophie has announced the second of its iPhone battery boosting range - the Juice Pack Plus - which it says will "more than double" your iPhone 4's battery life.

The "ultra thin and lightweight" device fits onto your iPhone 4 like a regular (if slightly fatter) case, and gives you an extended power time-frame thanks to its 2,000 mAh capacity battery, that you can charge up via USB.

With 3G on, you should get an extra 8 hours of talk with the Juice Pack Plus (2 more than the Air version) and double this if you're happy to go 2G only. You should get 44 hours more music playback, and 11 hours extra video.

If you're all about the web, have no fear - you'll get up to 7 additional hours internet use on 3G or 11 hours with your Wi-Fi switched on.

The case also works as a "virtual speaker box", with sound being redirected to the front of the device due to its shape.

There's an LED light display to tell you how much power you've got left in the tank and, like the Air version, you don't need to remove it to charge or sync your iPhone 4 due to the pass-through USB option.

The Mophie Juice Pack Plus is available now, in black, cyan, magenta or yellow, and will cost you £89.95.

See also - Mophie Juice Pack Air for iPhone 4 hands-on

And - Mophie Workbook hands-on