Battery problem with my iphone?

I have a problem with my iphone's battery. It drains even though I've locked it. Yesterday night the battery is still 83%, today it became 73%! I've tried auto lock, and I've tried reducing by brightness. Can you help? It happens a lot… Is it just my iphone?

That doesn't sound like anything wrong. There are tons of apps that could be running in the background, without you knowing, that use battery power. The big ones are games that you didn't close down correctly, the others are email. Email checks regularly, depending on your settings, from every 5 minutes, to manually only. If your programs are checking for data all the time, a 10% usage, over night, is not a big deal at all. Now if you have a completely wiped phone with nothing on it, including apps or email, and it's draining that much overnight, while in airplane mode, then yes, I'd call and get a battery diagnostics done. It takes just a minute or two, and will let you know if your battery is running fine or not. It's also free to have it done, just call 1800MYAPPLE, and ask for a battery diagnostics, because you think your battery life isn't what it's supposed to be.

Editing, because I forgot to walk you through shutting down the apps fully. On the home screen, press the home button twice. This pulls up your multitasking, showing you four apps at a time that are still running. Hold down on one until they start shaking, then click on the red minus sign in the corner, which shuts the app down fully. Most people don't know about this, and are shocked at how many apps are running in the background.

I would agree with Jennifer and she covered a lot of information about your battery However, I have never heard of apple performing a Battery Diagnostic. You can call them for support at no charge within the first 30 days of ownership of your device. After that, you have to pay $29.00. If you need help with shutting down your apps, or how to go through other settings that would help extend battery life, feel free to contact me at easysmartphonesupport.com. I troubleshoot Apple iPhones, iPads and iPod touches all for only $10.00. You can call at 888-506-4448, or email at techhelp@easysmartphonesupport.com Look forward to hearing from you.