Over the last few months I ‘ve been enjoying running my iPhone jailbroken more than ever.  It helps that I ‘m using a 3GS and the stability and speed of the thing just keep on rocking almost no matter what you throw at it. One area that does not necessarily keep rocking quite as well […]
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Jailbreak, Backgrounding Apps & iPhone Battery Life

Dec 27th 2009 by

SBSDisplay

Over the last few months I ‘ve been enjoying running my iPhone jailbroken more than ever.  It helps that I ‘m using a 3GS and the stability and speed of the thing just keep on rocking almost no matter what you throw at it.

One area that does not necessarily keep rocking quite as well is battery life.  Just as with running an iPhone ‘stock ‘ (without jailbreaking it), there are numerous factors that come into play when measuring how good your battery life performance is. It generally takes a little effort and tweaking to get something like optimum battery performance.

Since backgrounding apps and rapid app switching are right at the very top of my reasons for being jailbroken, I ‘m keen to see the impact they have on battery life as they have become a constant for me in my everyday use of the iPhone.

Yesterday we took a quick trip from Austin to about halfway to the Dallas Fort Worth area (to Lorena) to meet up with my wife ‘s parents, for a quick late lunch and then a hand off of our daughter to spend a few days with her grandparents.

This seemed a good day to do a little battery monitoring, as we ‘d be spending quite a few hours in the car “ so I left the Mophie Juice Pack Air at home and ignored the car charger and gave backgrounding apps and 3GS battery life a little spin.

Here are some notes, and then some quick conclusions, on the experience:

My iPhone 3GS battery-related settings were like this during yesterday ‘s trip:

  • 3G turned On
  • WiFi Off – as we wouldn ‘t be going anywhere likely to have hotspots to make use of, and I prefer not to run 3G and WiFi concurrently
  • Location Services On “ always on in case the phone is lost
  • Bluetooth Off
  • Brightness set to about halfway and to auto-adjust, as always
  • SSH Off
  • Firewall Off, as always except directly after adding a new app

And here ‘s a rough rundown of how I used the iPhone throughout the day and evening when back at home:

  • During the almost two-hour outbound trip, I was checking email occasionally, tweeting a bit, reading RSS feeds, checking out certain articles in Safari, peeking at site stats once in a while, and freqently checking the Maps app to see how traffic was and how we were progressing towards our meeting point. Oh, and taking notes on battery percentage and usage.
  • So I was running between 4-7 apps backgrounded at various points of the day “ including Newsstand, Safari, PhatNotes, Tweetie, iPod, Pandora, and Maps “ and using ProSwitcher to swap between them.
  • I also, as always, had QuickDo and SBSettings running “ for quick access to favorite apps, and settings toggles.
  • Also, as always, I was running the PogoPlank springboard replacement.
  • I didn ‘t use the iPhone at all during our lunch in Lorena
  • My usage pattern on the 2 hour trip home (traffic was worse on the way back) was much the same as on the way out, with a little streaming music via iTunes and Pandora thrown in
  • Once we were back at home, I kicked back in front of the TV and used the iPhone during commercials to check mail once in a while, read RSS feeds, look around the App Store and Cydia a bit, and check out BuddyFeed (for Friendfeed access) and Tweetie 2 occasionally as well.

Here ‘s how battery percentage fared during the day and evening:

1:45 PM: 92% “ just setting off on our trip

2:52 PM: 80% “ down 12% in a little over an hour of moderate-to-heavy usage

4:15 PM: 71% “ down 21% in 2.5 hours

5:45 PM: 61% “ down 31% in four hours

6:45 PM: 51% “ down 41% in five hours

10:45 PM: 34% “ down 58% in nine hours

Some Quick Thoughts on Battery Performance:

I think overall the 3GS did quite well.  Going down by 58% over nine hours of moderate to heavy usage, and still having 34% left after starting with a not-quite-full tank, seems perfectly acceptable to me.

Now I did not run any powerful games, or watch any videos during my nine hours of use.  Those sort of activities would likely have burned through the battery percentage far more quickly “ but the truth is those are not things I do that often anyway on a typical day of iPhone use. 

My finger-in-the-air measure of battery life performance for smartphones has always been ‘does it make it through a business day? ‘.  Yesterday ‘s performance for the 3GS shows the battery diminishing at a rate of less than 10% per hour.  That gets you through a 9-10 hour business day I ‘d say, if your usage habits are anywhere close to mine.

Of course, your mileage may vary “ a whole lot “ depending on your own usage patterns, and your settings.

One very positive result is that backgrounding apps does not seem to cause a big hit on battery life.  Running 4-7 apps backgrounded throughout the day and evening really does not seem to have had much impact.

Then again, this was only a one-day experiment, and I imagine results might vary a lot depending on what sort of apps are kept running in the background.  For instance, I imagine that any apps that do a lot of continuous talking to a remote server would be a big drainers (like certain online games).

Even so, I find this very encouraging – as backgrounding and app switching are a flat-out essential to me by now.

I plan to continue to monitor how nicely (or not) backgrounding and battery life are playing together on my 3GS.  I ‘d love to hear your thoughts and experiences in the comments.

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