Smartphones are the Swiss Army Knives of the tech world: they're cell phones, music and video players, mobile Web browsers, personal organizers...When you depend on your smartphone for so much, the last thing you want is for it to run out of juice when you need it most. Whether because they scored well in our CNET Labs battery tests or simply gave great usage time, these four smartphones really impressed us. ©2014 CBS Interactive Inc., a CBS Company. All rights reserved. Used by permission.