If you’re an active and on-the-go iPhone 4 user, making sure your battery is always charged is a necessity. Having to make an important phone call, play that song, or send that last minute email or text message only to be greeted by a black screen is extremely frustrating. Sure, using a car charger can certainly help guarantee you make it through your day. But, what if you’re away from your car?

This is where the Exolife iPhone 4 Rechargeable Battery Case from Exogear makes itself known as the “Johnny on the spot” of charging solutions. The Exolife is always with you and your phone because it doubles as a protective case. This ensures that you will never be without your phone due to battery drain. In our testing, we found that the Exolife’s 1500mAh battery adds anywhere from 2-3 times the battery life to your iPhone 4, (which has a 1420mAh battery).

Previous generations of this type of rechargeable battery case design led to greatly impaired reception and signal quality. Exogear remedies this issue with their patented Exoclear technology, that guarantees no signal loss or degradation of any kind caused by the Exolife case. This was a huge problem with competitors’ solutions for the iPhone 3G and 3Gs, so this is a great relief.

The case is a two-piece system that consists of the base for the phone to slide into and a snap on bumper-like trim piece to keep your phone both secure and protected. While the extra built-in battery does add bulk to your phone (to be expected), Exogear claims that it is the thinnest and lightest solution available.

Overall, we strongly recommend the Exolife case for your iPhone 4. With it’s tank-like build and negligible addition in weight, it is something that we’ll be using each and every day.

The Exolife Rechargeable Battery Case can be purchased at Exogear for $89.95 and is occasionally offered at lower prices on Amazon