I had to travel recently and put iPhone 4 on airplane mode and turned it off. When I turned it back on at the end of my journey and started using my phone in a regular manner nothing over the top the battery was draining before my eyes. 5%in three minutes and it just kept going. I don't know what I have done I have to constantly charge it if I want it to last the day of general usage - emails, web checking etc. can anybody help.
Check your battery. You may need a new one. Here's how to check your battery.
Go to Settings>General>Usage
Write down your usage and standby time, press the sleep/wake button (or lock button, as some call it) to put the device to sleep, and set the device down for five minutes. When you come back, take note of the change in time. If your device is sleeping properly, then the Standby time should have increased by five minutes and your Usage time by <1 minute . If your Usage time rises by more than one minute, you have a drain problem. Something is keeping your device from sleeping properly, significantly shortening the time it will last.
Let us know the results. If it's not a bad battery, there may be another fix.
Sent from from my iPhone 5