I'm experiencing significant battery drain with my new iPhone 5 when in standby mode--much worse than my iPhone 4. Last night, I charged both my iPhone 4 (running iOS 5) and iPhone 5 (iOS 6) to full capacity and let them sit idle for eight hours while I slept. When I woke up, the iPhone 4 was at 100% and the 5 was at 78%. Both had the same apps and options enabled (Bluetooth on, Wi-Fi on, brightness set at same level, etc.) The only difference besides the iOS version is that the 5 was connected to a cellular network when the 4 was not. What accounts for such drastic differences? And is there any known fix?