No matter what smartphone you own, chances are its run out of juice at least once sometime when you needed it. There are tons of backup battery options out there to help you keep your phone powered up for the long haul, but with so many options it can be difficult to determine which one might be right for you.

To help make that decision a little easier I'll be checking out some of the best options out there, and giving you the low down on what works well, and what doesn't.

Mophie Juice Pack Air

Mophie was nice enough to send me a Juice Pack Air (and a few other battery options we'll check out later) right before I headed to CES in January. The Juice Pack Air is a case for your iPhone, that has a battery built-in to its bottom. The case can virtually double the battery life you might traditionally get from your phone.

Advantages I love that in the case of the Air the battery is also a case. No matter how big your purse (or pocket) is, carrying some of the larger extendable batteries can be a bit of a hassle. The Air just makes your phone itself a little larger, which makes carrying around the extra battery a little easier. The battery pack can be charged while its on the phone, so you can put the case on and just charge both each night when it comes time to plug in.

So you're not just charging up all the time, the bottom of the JuicePack Air has a standby switch that can be turned on and off. So, when your phone battery starts to get low, you can just switch on the backup battery on your case and start charging. I used the Juice Pack Air for the first few days of CES, which involved texting, tweeting, and checking email pretty much constantly from 7am-midnight everyday and never once ran out of power.

Disadvantages While the Juice Pack Air has "Air" on the end of it, it's anything but small. I felt like the case made my iPhone huge.  So huge in fact that I had trouble getting it in and out of pockets (albeit pockets on my girl jeans), and some/most of those tight-pocket times ended in me leaving one side of the case behind in my pocket. The substantial size and lack of ability to physically keep the case together were two huge failings for me. Chatting with a few other phone bloggers at the show, it sounds like I'm not the only one that's had trouble getting the case to stay together

I've also found that carrying around other types of portable charges typically ends in my not only charging my phone, but also sharing my juice with friends who need a little extra power, as well as occasionally charging things like my iPad or other electronics. Since the Juice Pack Air is built into an iPhone case, you're only going to be able to use it for an iPhone. Along those same lines, if you buy an iPhone 4 cases and then decide to switch to an Android phone or upgrade your iPhone, you're likely going to have to invest in another Mophie case as well.

Overall If you're looking for a backup battery that you can tote around with you whenever you are, and don't mind carrying around a slightly larger phone, then the Mophie Juice Pack Air can be an excellent choice. If you're prone to wearing clothes with small pockets, or want to be able to charge more than just your iPhone with you backup battery, then you'll be better off picking up an alternative.

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