Need more battery juices for your iPhone 3G at no cost? SlashGear, PhoneMag and iPhoneBuzz are giving away one Mophie Juice Pack Air each. Check out each sites for the contest detail!

Juice Pack Air features an innovative “standby mode” that allows users to control when they want to take advantage of additional battery support versus simply using it as a protective case. The integrated 4 LED charge status indicates how much power is remaining in the external battery. Unique pass-through design allows users to simultaneously charge their Juice Pack Air and sync their iPhone 3G with iTunes via the included USB cable.

Additional battery time provided by Juice Pack Air:

* Standby Time: Up to 270 hours
* Talk Time: Up to 4.5 hours (3G) Up to 9 hours (2G)
* Internet Use: Up to 4.5 hours (3G) Up to 5.4 Hours (Wi-Fi)
* Audio Playback: Up to 20 hour
* Video Playback: Up to 6 hours