It’s safe to say that your iPhone is much more than just a phone – it’s your camera, planner, address book, GPS, and anything else you may use it for. That said, your iPhone is only useful when it’s powered on. With the introduction of iOS 5 (or for some, the iPhone 4S itself), many users have suffered some battery issues. While iOS 5.1 purportedly fixes these issues, the problem persists for many.

So what do you do when your iPhone, your do-it-all device, starts dying on you while you’re away from home? The first steps you can take to avoid a quickly depleted battery are in this article. Otherwise, you can carry a wall charger with you, or use an in-car charger. If you’re away from both, then a battery case is your best bet. Today we round up five battery cases that will give your iPhone 4 or 4S the juice it needs when you need it most.

Juice Pack Plus by Mophie ($99.95)

Juice Pack Plus by Mophie

Mophie’s Juice Pack Plus is perhaps the most well-known iPhone battery case available, and for good reason. It packs a 2,000 mAh battery (up from the iPhone 4 and 4S handset’s 1,420 mAh and 1,432 mAh, respectively) that will more than double your iPhone’s battery life. This case features a standby switch that allows you to choose when you want it to charge your phone. Four LEDs on the bottom of the case indicate how much power is left. Available in black, white, cyan, pink, yellow, purple, and red.

Elite by PhoneSuit ($79.95)

Elite by PhoneSuit

PhoneSuit’s Elite case is “the thinnest, fastest iPhone 4 battery case to provide over 100 percent power.” Its slim design (0.67 inches thick compared to Mophie’s 0.71) still manages to provide full protection for your iPhone. The Elite packs a 2,100 mAh battery that promises to fully charge your iPhone in two hours. A battery light meter indicates the case’s remaining power status. Like the Juice Pack Plus, the PhoneSuit Elite can be powered on or off at will, ensuring you’ll get the most from the case. Available in black and white.

Boost Case Plus by Boostcase ($79.95)

Boost Case Plus by Boostcase

This simple, but effective case features a whopping 2,200 mAh battery and will automatically detect your iPhone to toggle on or off accordingly. Of course, you can manually activate the case, as well. The Boost Case Plus is built from a durable easy-grip protective shell, which makes it feel like a protective case, while providing the benefits of a battery case.

Mojo Removable Battery Case by ibattz (Starting at $69.95 on Amazon)

Mojo Removable Battery Case by ibattz

The Mojo Case by iBatts features two removable 1,500 mAh BP-4L batteries – each capable of providing up to an 85 percent charge to your iPhone. The case is composed of the battery housing which only covers the back and bottom of the phone, while an included bumper covers the rest. Available in black and white.

Power Rock by New Trent ($34.95)

Power Rock by New Trent

Definitely the least flattering case of the bunch, New Trent’s Power Rock case features a 2,200 mAh battery that will more than double your iPhone’s battery life. This affordable battery case will definitely get the job done, but may not look the best while doing it. Available in black.

Each battery case in this roundup uses micro USB to both charge and sync your phone to iTunes. Once you get past appearances, these cases all promise you the same thing: increased battery life for your iPhone. More information on each case can be seen by clicking the links above each picture, and a plethora of customer reviews (and potentially lower prices) can be found on Amazon.

Was this list of iPhone 4/4S battery cases helpful to you? Are there any we left out?