Here's how can disable LTE to extend your iPhone 5's battery life.
1. Open the Settings app.
2. Tap on General.
3. Tap on Cellular.
4. Toggle the Enable LTE switch to the Off position.
By turning off LTE, you'll help extend the time between battery charges on your iPhone 5. LTE is very fast and useful, but why have it on if you aren't using it? It just wastes the battery.