We have introduced many nice protective cases with backup battery. But if you want to freely change battery for a longer battery life, uNu Ex-Era modular iPhone 4 battery case may be able to draw your more attention.
The Ex-Era is a versatile, modular protective case that measures 120 x 62 x 18mm, and designed for iPhone 4 and iPhone 4S. The iPhone 4S case is constructed of lithium polymer in order to protect the iPhone 4 or 4S from bumps and scratches, and the accompanying 1700mAh backup battery can double the battery life of your iPhone, while its unique swappable design gives you a chance to offer more juice for your iPhone. Moreover, when not in use, you can also replace the back cover with backup battery with an additional ultra-thin back cover for slim look. Apart from that, all the buttons and functions are accessible via custom cutouts.
uNu Ex-Era modular iPhone 4 case with backup battery is priced at $79.95 USD. If you’re interested, jump to uNu official site for more details or check out the following demo video first.
Additionally, if you need other options, you might like to check ClickMate PowerPlus iPhone 4 case and more via “iPhone 4 case” tag.