Passbook for iPhone may be a great tool for managing boarding passes, reward cards, and more, but it can also be a drain on battery. Since Passbook continuously checks your location to see if you're in range of somewhere you may want to use one of your passes, it can significantly decrease your battery life.
While it's a convenient feature, if you're finding your battery life is suffering, you can disable location services to lessen the strain on your battery.
That's it. Passbook will now stop searching for locations where you have passes. The down side is your passes will no longer show on your lock screen, meaning you'll have to manually open Passbook to use them. The bright side is that you'll probably get a little more battery life out of your iPhone. You can, as always, return into settings and re-enable the feature anytime you'd like.