On my Google Nexus 7 I noticed that it would consume around 1% of battery each hour that it was just being idle. I suspected that battery-usage during idle time could be improved. So the next night (7 hours) I put my Nexus into airplane mode, and the next morning the battery had only used 1% for those 7 hours, which proved that there was room for improvement.
Next I disabled bluetooth and set wi-fi, to be disabled when the screen is locked (changed "Keep Wi-Fi on during sleep" from "Always" to "Only when plugged in"). After a fews tests of 7 hours idle the battery was down 2 ~ 3% each time. But then I noticed in the battery graph, that the wi-fi still showed quite a lot of activity. This probably explains the difference in battery consumption with airplane-mode.
I had expected the wi-fi to be completely disabled with this setting, and the wi-fi bar in the battery graph to be almost completely black. To see the difference I manually disabled the wi-fi and then the bar is indeed completely black (the right block in the image): enter image description here

I would expect the wi-fi to be completely off when the screen is locked, but looking at this question: Turning on Wi-Fi on demand that is apparently not how Android works. So now I'm wondering what the wi-fi is doing in this setting? Why does Android keep the wi-fi 'partly' enabled? If Android would still let apps do their syncing etc on a regular basis I would understand this, but this is not the case (Notifications don't come in & it even seems to cut off streaming etc), so it seems to only waste battery?

I first suspected a misbehaving app, but I checked with Wake lock detector and Network log but don't see any suspicious apps. I guess I could use JuiceDefender or a similar app to completely disable the wi-fi when the screen is locked (and still let it sync from time to time), but that's not really the point of this question.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.