Jul 10, 2009
iPhone OS 3.0: Push notifications might be killing your battery
iPhone OS 3.0 brought with it a slew of new functionality, and some hidden gems. copy & paste, extended battery life, and push notifications were the three that piqued my interest most of all. after upgrading, i was happy to find that copy & paste worked well enough, and i actually found improved battery performance post upgrade. life was good. admittedly, i was a little disappointed that apps like AOL Messenger were not ready to go with push notifications right out the gate.
a little less than two weeks ago i noticed that my iPhone 3G was refusing to charge beyond 20%. the main battery indicator displayed 20%, and the indicator in the upper right displayed the “plugged in” battery symbol. definitely a mixed signal.
i decided to wipe the iPhone, do a full restore, and see if this improved things. after doing so, the iPhone accepted a full charge, and the next day we embarked on a trip to San Francisco via Caltrain. a few hours after leaving, and with very little use on the iPhone, the battery displayed 50% charge (and draining quickly). a couple notes on my settings before someone chimes in on with suggestions:
- brightness is ~30%
- 3G is off
- WIFI is off unless i’m in an area with known access
- push mail is on, but only for exchange. all other accounts are set to fetch
by the time we reached our destination the iPhone was well below 20%, so we decided to make a pit-stop at the apple store for a visit to the genius bar. after a short wait, the apple tech ran some tests on the iPhone, and then promptly replaced it with a new one.
back at home, i upgraded the OS to 3.0, then restored from a backup. things seemed to be going better, in that i could at least charge the iPhone without problems, however the battery drained quicker than i’d remembered prior to 3.0. over the next week, the iPhone’s battery life continued to dwindle in performance, and the mixed signal issues from the first round started up again.
this time i tested the iPhone charging behavior a little more. i noticed that unplugging and replugging the iPhone back in could eventually trigger a charge cycle. so, i left the iPhone on the charger for several hours only to return to find it was completely drained of battery. next, i decided to test different charging scenarios: plugged into a computer, directly plugged into the wall, and using different cables. all of this made no difference.
on the verge of yet another wipe and restore attempt, i happened to notice something that opened up another possibility. i received a push notification from foursquare while charging (with the charge indicator displaying the lightning bolt symbol). after i read the notification, something caught my eye — the lightning bolt in the upper right was now replaced with the “plugged in” symbol. to top it off, the push notification (when the phone was left locked) kept the iPhone’s display on. i monitored this for roughly 10 minutes, and the screen never went back into sleep mode. sure enough, the battery was draining steadily.
it’s completely reasonable to expect push notifications to have some impact on battery life, but this appears to be a bigger functionality issue. i’m not seeing the same behavior with other notifications (like text messages, missed calls, or voicemails). for now, i’m keeping push notifications turned off until the v.3.1 update to the OS drops. of course, this might not be the same for all. i’ve found that some people reporting the opposite case (push mail causing the drain, not push notifications).
i’ve tested the phone for 2 days since removing push notifications, and battery life is back to the “improved” levels from before enabling push notifications. i’ve yet to bump into any of the odd charging state confusions, and i’ve also been able to heavily use the phone while commuting on Caltrain with only a 25% loss of battery (this was unheard of on the 2.0 software).
anyone else experience similar issues?