Everyone I know with an iPhone is constantly complaining about running out of juice. I’m no exception. I finally threw in the towel and decided to get a removable battery case, so I can extend the life of my phone.

I read a number of online reviews, and the ibattz Mojo REFUEL and REFUEL ARMOR Removable Battery Cases came highly recommend, so I thought I’d start with them. I’m happy to say that they lived up to my expectations. The design is solid, and the battery case is light and slim. Taking the case on and off is a breeze. ibattz also improved Mojo’s battery, replacing last year’s 1700mAh replaceable batteries with 2200mAh batteries.

If you go for the ARMOR version, which costs more, you get a choice between a super rugged case that looks like you can drop it off a cliff without a problem, and a slimmer case that I actually prefer. In my opinion, the rugged case is just too thick and awkward, while the slim case fits nicely in your hand and pocket.

If you’re like me, you can save some money by buying the ibattz Mojo REFUEL, which comes with only the slim case. However, if you don’t mind spending a few extra bucks, then you can easily switch between the two cases depending on what you’re doing with your phone.

From my simple tests, the 2200mAh cells delivered at least a 100% (or 200% total) recharge for a fully discharged iPhone, which is pretty darn good. This means the Mojo Refuel delivers more power with just one of its included batteries than a more expensive Mophie Juice Pack Air.

The only downside I can see to these cases is that they aren’t as sleek and beautiful as other cases on the market. They are by no means ugly. In fact, the slim case looks nice. But it’s safe to say that ibattz put more TLC into the functionality than the style — especially on the rugged case. So if you prefer brawn over beauty, this is the battery case you should go for.

NOTE: We received free samples of their products for this review.