There are already a few choices when it comes to battery cases for the power hungry iPhone 4, like the Exolife Exogear, the Mophie Juice Pack Air, and the Mili PowerSpring. But now comes a new challenge:, the Aigo aiPower i616.

Aigo claims to be able to double your battery life with this new aiPower i616. The i616 has a hidden USB ribbon cable for both charging and data built right into the case. Should you want for a longer sync cable than it provides on its own, there’s also a second microUSB port built into the left side, as well as a switch for the external 1500mAh battery and a handy button to display its current level of charge. The aiPower i616 comes with the MSRP of $80.

There’s also the cheaper InCase Snap Battery if you want to save that $20. It adds a 900mAh battery in a soft-touch frame that InCase claims is the slimmest around. The case doesn’t seem to give a sufficient protection to the phone as it only covers the corners and rear of the phone, and is too slim to give any sense of security. But the good thing is that it keeps the sleek look of the phone.

SOURCE via Aigo