Hello, RachelRose226,
It sounds like your iPhone battery indicates it is at full charge, but turns off when disconnected from power. I would next try backing up your phone to iTunes on your computer with this article to backup your data first:
iOS: Back up and restore your iOS device with iCloud or iTunes
http://support.apple.com/kb/ht1766
Then Restore it as a new device with the following article to see if the issue persists to isolate it to either software, if this resolves the issue, or hardware if it does not:
Use iTunes to restore your iOS device to factory settings
http://support.apple.com/kb/ht1414
If it is not resolved after the restore, the phone will need service:
https://www.apple.com/support/iphone/repair/battery-power/
Your Apple One Year Limited Warrantyincludes replacement coverage for a defective battery, and there is no charge if your iPhone is covered under warranty or an AppleCare product. You can check your coverage by entering your iPhone serial number.
All iPhone models: $79 |
Plus a $6.95 shipping fee. Fees are in USD and exclude local tax. |
Thank you for using Apple Support Communities.
Take care,
Sterling