BOYS AND GIRLS:
I HAD this problem until today... and working with AppleCare and the genius(es) at the Apple Store NYC/Upper West Side, we may have a solution.
Here's my story:
New iPhone 5 ATT 32gb opened the box on Tuesday @ 10am. Came with 60% charge. I RESTORED from my backup in iTunes (mac) - previously had an iphone 4, iOS 5.x
After RESTORING my backup to the new iPhone5, I let it charge to 100% via USB/lightning.
Like you, I noticed that battery life sucked. Hmm... must be (siri, maps, location services, retina display, insert any mythological user of battery power). By the following day (thursday), I recognized that something wasn't right. Burning way to much juice. Fortunately, genius appointments were avail later thursday afternoon.
Thursday's genius did a hardware diagnostic and then played with some settings... asked me if I had RESTORED from an iOS 5.x backup ... "yes" - genius asked me to WIPE the phone. Restore to factory, and DO NOT use the backup. Fortunately, my icloud and email accounts were all in iTunes and this only cost me 2 hrs. We can debate the inconvenience all night long, but I'd rather have a phone that works and I'm not a complainer.
By Thursday bedtime, the "rebuild" was back to my liking, and all media transferred. Still had to download iTunes match music. Next time, I'll have a playlist for all of my matched music. I charged the phone overnight and when I woke up at 6:45 am, the phone was 100%. Great. I went to work.
Friday, I used the phone for some texts, listened to some music on the way to work, made about 10 minutes fo calls, used siri a few times, read a bunch of email, etc... normal morning use of a mobile device. But by 11am, I didn't like that the usage was starting to come down. And I noticed that the "General > Usage > Time since last full charge:"
is identical -- genius told me that we want to see some delta here... these numbers should not be the same. By the time I saw Friday's genius, the numbers were both at 8hrs+ -- exact match.
Friday genius again did a hardware diagnostic, then took a look at the crash log... he said that something must have crashed during the config... and yes, the appstore crashed when I was updating 135 apps. I failed to restart the iPhone. Friday genius restarted the iphone then put the phone to sleep. He told me to sit tight for 10 minutes. 10 minutes later - there was a delta between standby time and usage! He pointed out the crash logs... and it looks like an app crash took out the battery manager. THIS ALSO EXPLAINS why the battery was charging at rapidly fast (unusually fast) speeds. Friday genius said the official time to charge an iPhone5 should be about 80 minutes from 5%. If it charges from 50% to 100% in 10 minutes, something is not right. And what's not right is the battery/power management software is crashing.
THIS IS ENTIRELY a SOFTWARE ISSUE
Many of us have apps crash and we simply keep using the phone -- but Friday genius instructed me to do a hard reboot to be safe.
I am now charging and I will report back if all this is still working later.
SUMMARY - to make this work:
1. DO NOT use restore from previous backup. WIPE your new phone and configure from scratch. YOU CAN use mail and iCloud settings sent from iTunes;
2. AFTER you sync in iTunes, RESTART/REBOOT your phone
3. Verify that "Settings > General > Usage > Time since last full charge:" has delta from standby to usage (after sitting there for a few minute in sleep).
I think this will solve our issue(s) - which seem to all be related.
PLEASE, PLEASE, PLEASE state and confirm in future posts that you have:
1. WIPED your phone
2. You DID NOT restore from a backup
3. You rebooted your phone after the sync/config
4. There is a difference between standby to usage times in Usage settings
If you have not done ALL FOUR of these things, your contribution to this thread is not useful to Apple. And yes, they are monitoring it, so please keep it professional. Thanks to all.