Exolife Battery case is a slim battery pack + sturdy polycarbonate frame case complete with illuminated power meter. It’s unknown yet whether if Exolife Battery case can double up the battery life of your iPhone 4, but at least this battery pack case is very lightweight and slim design. It won’t give you any burden (it’s 59 grams only) even there is an extra rechargeable Lithium polymer battery install on your iPhone 4.
Exolife battery case will cost you $90 to own one. If you think your iPhone 4 battery life is too short for you, this exolife battery case might be just for you!