We have introduced many practical iPhone 4 cases with integrated backup batteries. But if you want larger battery capacity, the following Incipio offGRID PRO backup battery iPhone 4 case may be more suitable for you.
The offGRID PRO is a practical form-fitting battery case that measures 5 x 2.75 x 0.57 inches, weights 2.4 oz, and designed for iPhone 4 and iPhone 4S. The iPhone 4S case features solid polycarbonate construction in order to protect the iPhone 4 or 4S from bumps and scratches, and comes with a set of two interchangeable and rechargeable backup batteries with 1600mAh of charging capacity each, so you can easily triple the battery capacity of your iPhone 4 when you’re on the go, while the LED indicator shows you the battery status. Apart from that, the custom cutouts allow you access to all the buttons and functions of your iPhone 4.
The offGRID PRO iPhone 4 case is available in three colors including black, gray and white, each one is priced at $99.99 USD. If you’re interested, jump to Incipio official site for more details.