Disabling LTE on iPhone 5 will save battery’s life much better, especially when you’re out of LTE coverage.
How-to disable LTE on iPhone 5?
Tap Settings → General → Cellular → Enable LTE.
Toggle the Enable LTE option to turn off LTE connection on your iPhone 5.
If you want to turn the LTE back, you’ll just need to toggle the Enable LTE option to turn it ON.