Sunday, October 26, 2008

iPhone Battery Life Tests

Last night I was able, for the first time, to test the theory that the iPhone consumes significantly more power when doing 'push' sync with our service. I left a fully charged iPhone on a shelf in a location with 5 bars ATT 3G service, and push enabled (which is the default configuration). This morning, after 12 hours on the shelf, the iPhone's battery level indicator was still at 'full'. At first I suspected that it wasn't actually syncing so I pulled the server log records for the device. These indicated that the phone had completed a 'ping' sync operation roughly every 7 minutes all night, which is exactly what we'd expect it to do. In previous investigations, when users have reported increased battery drain over night, the server logs showed exactly the same thing: normal regular pinging.
Although this is a single data point, it does tell me that whatever is leading to the reports we see of significantly increased batter life is probably a function of the cell radio in the phone, rather than the sync client or some strange interaction with our service. Perhaps when it's in a location with marginal service it burns much more power sending packets or flipping back and forth between towers, for example.
I'm keen to dig deeper into this mystery and to do so we'll need reports from users who either do or do not see major battery drain from an otherwise idle iPhone that's using push sync. Please send any reports to with subject 'iPhone Battery Drain Investigation'.


Henning Vestergaard said...

Exciting experiment, and nice explanation with the cell towers!
I turned push off, as I experienced too short battery life leaving it on, however it may be subjective.

VPN and wifi on university is the big power drainer here though.

Mark Riffey said...


Do you guys have ATT service in Bozeman?

Mark in Columbia Falls

Thomas said...

I own one of the original iPhones. I upgraded to the 2.0 operating system about 3 weeks after it came out. About 4-5 weeks ago my company turned on Push email on our Exchange server for the iPhone so I enabled the Push service on my phone. I noticed the battery would drain in about 12-14 hours. I had Wi-fi turned off and we only get the EDGE network where I live. After a few days of it draining the battery I turned off PUSH. However, once the latest Apple iPhone software was released it said that it fixed a bug in the battery life. So I turned push back on and am not experiencing any issues with battery life. So, if you haven't done it, you may want to verify that you're up to date on the Apple iPhone Software.

Hope that helps

Ipfix said...

you're doing a really good job.
Thank you very much.


Jordie said...

Hello all. Just thought i would pipe up and let you know my thoughts. I am a fairly heavy user of the calendar, mind you its mostly pushing from my iPhone to Google. I havent noticed anything odd about battery life other than its poor to start with. I have Wi-fi on, 3G on and am talking on it for about 3 hrs a day and need a top-up about lunchtime.

Hope that helps. Im running 2.1 firmware.

Still holding out for those multiple calendars you guys keep on promising ;)

BrokenBones said...

Off topic, but another person checking in twice a day for multiple calendar support. Myself and my two partners have been waiting on this to join.


Jens said...

I own one of the 1st generation iPhones and am experiencing some problems with the iPhone sometimes discharging over night.

As the WIFI connection in my bedroom is not that good, I assume it has to do with that.

I will test how it performs when I leave my iPhone near my WIFI access point.


David Boreham said...

Some answers:
If you take an iPhone to Bozeman, you'll get service including Edge data. ATT does not sell service in Montana, hence presumably service is delivered via roaming agreement with one of the local GSM providers.
However, the test I mentioned was done in LA (Orange County actually), on 3G native ATT service.

Kevin said...

Just an update - my battery life has actually improved.
Not sure if you guys updated the code, but I seem to be getting more juice out of my device recently.
Can't wait for the release of Apple's software update, and the permanent freeze fix (and perhaps multiple calendar support and push gMail)!
Keep up the good work.

Bruno said...

Hello David,

I own one of the 1st generation and I experienced also a shortened battery life with push on.
After several tries, I suspect a problem when push uses internet connection through a Wifi network.
No problem arises when I use push being disconnected from my Wifi network.
I can also stay connected to Wifi at home but in this case I've to disallow push or my battery life drops significantly.

Hope this helps

Jason said...

I get similar results to Bruno. As soon as I enabled push at home (where I have wifi) for my contacts and calendar, my batery life dropped like a rock (and I was about 10 feet from my wifi router)! I watched a program for 45 minutes and my battery dropped 20% with my phone just sitting there doing nothing. I turned my wifi off and my battery life went back to normal. I basically just keep my wifi toggled off now, and just turn it on when I am going to download a large file.