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Unexpected source of iPhone battery drain iOS devices
Battery life with my iPhone 4S was very poor, and I finally discovered why: I'm using a battery extender case. The problem is that the phone considers that the case is a source of AC power, so if have iTunes Wi-Fi sync on - which only operates when your phone is plugged in - you'll be syncing more than you might expect, since your phone is technically plugged in.

The solution is to either turn off Wi-Fi sync, or use an external battery pack that has an on-off switch so that you can control when it is actually sending current to the phone.

[kirkmc adds: I guess this makes sense. Apple says that Wi-Fi sync occurs when "The iOS device is plugged in to power." But this should only occur if two other conditions are met: "iTunes is open on the computer," and "The iOS device and the computer are on the same Wi-Fi network." So I would think that if you're not on the same network as your Mac, then nothing should happen. Perhaps the phone is constantly searching for that Mac?]
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Unexpected source of iPhone battery drain
Authored by: lowbatteries on Mar 14, '12 08:22:48AM

iCloud backup could be an issue as well. It happens when "plugged in, locked, and connected to Wi-Fi".



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Unexpected source of iPhone battery drain
Authored by: davester on Mar 14, '12 11:12:39AM

I've found that the battery case for my iPad [which also has a stand] winds up being drained incredibly fast, even if the iPad is fully charged. I have to jig it so the plug isn't connected all the time, just so I can actually use it to extend the iPads usage.



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Unexpected source of iPhone battery drain
Authored by: soulbarn on Mar 14, '12 12:10:01PM

Thanks for running my hint; you're right, of course - the situation I described happens only when the machines are on the same network. Since i work at home, this is almost always for me.

The similar issue with iCloud backups, though, is network agnostic - and maybe a more critical source of drain, since a least in the case I described, there's a power outlet nearby and I don't really need the extended battery life as much (though the at-home drain is an issue because I want to leave the house with a full charge).



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Unexpected source of iPhone battery drain
Authored by: babaloo on Mar 14, '12 01:43:50PM

@kirkmc
Don't forget, your iPhone can be plugged into power without a Mac, simply by using something like a USB Power Adapter, which plugs into a wall outlet.



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Unexpected source of iPhone battery drain
Authored by: August on Mar 14, '12 09:04:08PM

My iPod syncs while unplugged. I uploaded to the latest IOS 5.1 before posting to test again, but it still syncs while unplugged from any power. So I don't believe the sync logic from Apple is working correctly yet.



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Unexpected source of iPhone battery drain
Authored by: August on Mar 14, '12 09:58:37PM

Ha! In doing some more research on the web, I found an article that contains a correction to the idea that wifi sync requires external power. Their correction is to note that only the backup to iCloud requires external power.
http://www.tuaw.com/2011/10/12/ios-5-features-wi-fi-sync/



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Unexpected source of iPhone battery drain
Authored by: kirkmc on Mar 15, '12 01:39:20AM

That's correct, but it syncs automatically when you plug it in. I see this when I connect mine to a charger.

---
Mac OS X Hints editor - Macworld senior contributor
http://www.mcelhearn.com



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Unexpected source of iPhone battery drain
Authored by: August on Mar 15, '12 08:18:18AM

It also syncs when you start-up iTunes. I found this to be a problem when switching between different iTunes libraries, only one of which I wanted the touch to be synced with. This was especially annoying when the touch was off in another room or was being used to stream Pandora to my stereo. My solution was to put the device in airplane mode while working with other iTunes libraries. Now that I think about it, maybe it is best for me to just disable the wifi synching as being inappropriate for my use of the device.



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