21
Aug
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Wireless charging is perhaps one of the best examples of true convenience. The simple act of setting your phone down meant its battery would begin refilling. No need to hunt for the end of a cable, no more time spent clumsily aligning plugs, and no more hassle with loose cords. When the Nexus 4 was announced, its stylish charging orb was supposed to spearhead a movement of wireless bliss. While the orb certainly had its advantages, it was a bit late to launch and carried a premium price. Nevertheless, Qi-compatible chargers began to find a home with Nexus 4 owners. Unfortunately, the update to Android 4.2.2 brought with it a wakelock bug that could seriously eat away at the battery life of Google's flagship phone after it had charged wirelessly.

Allow me to briefly explain wakelocks. They are part of a mechanism used by Android for power management, allowing applications to keep parts of the device awake while allowing other parts to go to sleep. This system is important for things like syncing email while the phone is not in use, or keeping the screen on while Maps is giving turn-by-turn directions. As necessary as this system may be, badly written apps and services have a tendency to misuse it, which contributes to the reputation of poor battery life in the Android ecosystem.

Unlike powering your phone through a wire, wireless chargers lack the ability to go into a low-power mode, often called trickle charging. Instead, the phone alternates between drawing power and living on the battery. Ideally, this will allow the battery to hover near to 100% without wasting electricity or damaging it from overcharging. The new code in Android 4.2.2 introduced a system for actively managing these continual changes and prevents the phone from regularly chiming every time the power pauses. You can probably guess where all of this is headed; a wakelock by the name of PowerManagerService.WirelessChargerDetector is used to keep the processor from falling asleep while this processing is quietly going on behind the scenes.

This finally brings us to the problem: the new wakelock isn't always released when the Nexus 4 leaves the charger. As a result, the processor is kept idling at 384 MHz, never allowed to enter a deep sleep, which drains the battery fairly rapidly. Several people are reporting that the Nexus 4 can normally last up to 2 days on a single charge. However, when this bug comes out of the woodwork, battery life often falls to 8-12 hours.

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While the issue seems to be more common for some people than others, no specific set of steps has been found to reliably replicate it. Reports in the AOSP Issue Tracker and the Google Product Forum indicate that the problem is not limited to any particular wireless charging pad, but a few people have seen inconsistent results between models. If you would like to test for this behavior on your own device, Better Battery Stats (XDA Thread) does an excellent job of tracking wakelocks and other power-hungry processes.

Despite first being reported 6 months ago with the rollout of Android 4.2.2, and then persisting into 4.3, the Android team has yet to formally confirm the issue or assign it to an engineer to be fixed. Thus far, Paul Wilcox (he is the public face of the product forum) has only acknowledged that the team is "still looking into it," but gives no further details. Of course, if you can contribute anything that may be helpful in solving this issue, head over to the forums and leave a comment.

For those affected by the issue, the only reliable method for clearing the bug is to reboot your phone. The wakelock will not reappear until a wireless charger is used again, so your Nexus 4 should be safe until it needs juice again. Of course, you can always return to using wired power until Google fixes this, but that kinda defeats the purpose of an expensive charging pad.

Thanks, Nick Hoadley and Jon Bross.

[AOSP Issue Tracker, Google Product Forum, AOSP code, XDA 1, 2]

Cody Toombs
Cody is a Software Engineer and Writer with a mildly overwhelming obsession with smartphones and the mobile world. If he’s been pulled away from the computer for any length of time, you might find him talking about cocktails and movies, sometimes resulting in the consumption of both.

  • Benjamin S.

    My battery problems started with 4.3 and I always charge via cable, so I guess there are more than one bug in that department.

    • Andrew

      I wrote about this here http://forum.xda-developers.com/showthread.php?t=2392155

      I was able to get rid of 100% wake time by cleaning cache (Settings - > Storage - > tap on Cache) and rebooting. Simply rebooting did not help me, waketock was reoccurring eventually I did cache trick two weeks ago, and wakelock does not happen since then. It is not a solution, just some sort of voodoo, when you try everything just in case, but it helped. Maybe just a coincidence.

      • Trina S

        Another kind of odd thing I tried that's worked to stop nplwakelock is to make sure the screen is on and unlocked right before you unplug from the cable. Next time it crops up, I'm going to try the cache clear, though! Thanks!

        • Andrew

          Wakelock I'm writing about it not NLP one. NLP is about network location, IIRC. There are more or less reliable fixes, including adjusting location reporting settings.

      • Rodalpho

        If betterbatterystats doesn't show "wirelesschargerdetector" under kernel wakelocks, you have a different issue.

        • Andrew

          Exactly.

  • Taco Monster

    This issue has been giving me indigestion ever since I got the damn wireless charger. With 4.3, it's at least become more consistent: There's invariably a wakelock after I take the phone off the charger. I've gone back to the cable now, and the tacos are sitting much more steadily in my belly. Or at least they would be, except that the phone now randomly shuts off at around 30-40%, doesn't turn on except when connected to the charger, and then tells me it somehow ate up all the battery in that 10 second interval.

    • http://www.androidpolice.com/ David Ruddock

      I think I have a solution to your problem.

      Pepto Bismol.

    • basteagow

      I had to get rid of my Nexus 4 because it would occasionally die/freeze while on the (wired) charger overnight, and my alarm wouldn't go off in the morning.

      • RobC

        I have had to buy a QI charger, as the USB has failed on an 11 month old Nexus 4 - so the only way to get a charge and power up so I can retrieve pics and then send back for replacement, - I have to say in my dilemma - it was the only thing that worked - the email for a "fix" from Google support didn't work so in desperation picked up a Nokia DT_900 if any one needs to get hold of one - discounted to £37 - didn't have time to wait for the £20 from china with no charger - O2 store seem to be the best bet for one - ( in Manchester)

  • nmaxfield

    surprised to see this is the first time this has been covered. i noticed this happening occasionally (maybe 1 in 5 times or so) a few months ago. i've only just updated to cm10.2 the other day as i had issues with other 4.3 roms, so i'll keep an eye on the wireless charging for a few days/weeks.

    • Matthew Fry

      This is the first time AP is covering Android bugs in significant numbers. Be happy that it's getting some attention. Google employees follow AP (unlike the *actual* product forums).

      • nmaxfield

        valid point *thumbs up*

      • http://www.androidpolice.com/author/cody-toombs/ Cody Toombs

        For what it's worth, I'm trying to focus on covering most of these in the name of helping users become aware of problems they should watch out for and hopefully provide short-term solutions or advice. In this one, for example, I doubt many people even realize their battery life could be crippled by using a wireless charger. Now some people will know to reboot their phones after charging or go back to a cable for a while.

        I'd like to think some of these articles will get some positive attention from Googlers and lead to some fixes, but I tend to think they are more aware of these bugs than people give them credit for. As a software engineer myself, I know what it's like when the managers have a list of 15 "high priority" projects standing between you and the list of 50 bugs that "can be fixed later."

        • Simon Belmont

          I appreciate this. A PSA for small bugs like this that make people go *slap forehead* "so THAT'S why my battery life is bad lately" are great.

          By the way, I totally agree with you on the bug list priority thing. Small ones, that can still call huge consternation in users, may be low priority compared to others (software developer here too).

  • mgamerz

    Too bad the Nexus 7 dock (2012) bug doesn't get fixed either. I pull it off half the time and it doesn't think I did so it doesn't play audio. Only solution is to reboot or put it back on the dock and pull it off again... That, and the clock crashes half of the time when docking.

    • Derek

      fyi. To remedy the audio problem you can go to audio settings and de-toggle Dock-Audio-ForMusicAndMedia

  • Andrew

    Unfortunately, with Android 4.3 it is not the only bug that can prevent your device from deep sleep. I have already posted link on my thread on XDA http://forum.xda-developers.com/showthread.php?t=2392155

    Since then there were not much of the development, just more reports from users of Android 4.3 on Nexus 4 and both 2012 and 2013 Nexus 7 devices.

  • linjef

    I definitely did see this show up in betterbatterystats both with the Nexus 4 and Nexus 7. It wasn't every time, though, which made it maddeningly frustrating. It happened last night, and I stumbled into the bugtracker, saw some posters say they reported it to AP, and now here it is!

  • Andy

    I've been living with this exact problem for 5 months now and it's driving me insane.

    I own the Nexus 4 and official charging orb. I charge overnight, and every morning i have to remember to reboot the phone right after i wake-up or else my battery drains. PowerManagerService.WirelessChargerDetector keeps the phone awake indefinitely as described in the article.

    Can't believe 4.3 didn't fix this bug.. This bug has been well documented since February.

    Meanwhile, a friend with the exact same phone and charger has no issues whatsoever.. go figure.

  • Magneira

    Funny that almost all android phones now lasts more than iphones and still people keep saying that android has poor battery life... lets see if this changes with ios 7 now that they will have true multitasking

    • Switcher

      Nope. Just come from an old iphone4 that comfortably lasted all day, to a nexus 4, brand new, needs charged before end of the day.

  • OmniWrench

    This isn't directly related to the article, but if part of the OS is managing the wireless charging cycle, what happens if one leaves their phone charging wirelessly while turned off? Every night I turn mine off, then place it on the orb... Am I potentially wasting power and/or overcharging?

  • Russ

    Apparently the 2013 N7 is affected too

  • Steve Secor

    This was intermittent for me in 4.2.2. Since 4.3 I've gotten this wakelock every single day. I also use standard daydream clock overnight.

    Monday, after the internet exploded about Timely; I decided to try it out. Using the Timely daydream last 2 days this wakelock hasn't appeared.

    Coincidence? Probably. But my battery life is insanely awesome on my phone without that wakelock showing up.

  • sidamos

    I do not have this wakelock and my N4 shuts the display off when it is 100% full, so I am seeing the exact opposite. This is really bad when you want to use the phone with Daydream as a night clock.

  • Simon Belmont

    Ouch. That's a nasty little bug.

    Hopefully the Android developers can figure it out. Perhaps put it out in the Android 4.3.1 update.

  • KathyJN

    I think I have the opposite problem. My N4 wakes up often while charging, which, at night (when I charge most often), means my phone lights up the room, goes to sleep, wakes, goes to sleep, etc. If it's not doing that, then it's losing charge while on the TYLT VU or the Orb, if I'm running Dashclock on Daydream. I have also tried Timely, which won't show night mode. I can't win. Is my wakelock not working at all?

    • Morgan

      This sleep wake, sleep wake loop happens to me as well. Did yo ever find a solution?

  • Tim242

    Wireless charging is a gimmick, and waste of energy. Because of the amount of energy lost, it takes double the time to charge. Not efficient in any way.

    • Sean Walton

      I use it at night only. Have the Orb on my bedside table and at night I just plunk it down. It is slow so during the day if I need juice fast I go to the cable.

      • Tim242

        Hopefully since you sleep with it beside your bed, you have it in airplane mode!

      • http://www.facebook.com/lucyparanormal Daniel Tiberius

        Same here, and I don't put it in airplane mode like Tim suggests, cause if someone is dying or something important is going on I'd like to get a call. I don't mind it charging slower, though it's not all that noticable of a difference for me. Slower charging is better for the battery from what I've read anyways.

    • Justin W

      It takes me 3.5 hours to fully charge from 10% my Nexus 4. It's roughly the same with my cable charger.

      • Tim242

        It's a proven, known fact that wireless charging is not efficient, due to the amount of energy lost. There is more voltage going in from the cord. I'm not sure why you are trying to convince otherwise.

        • Justin W

          Hit submit too early, but my point is it is less efficient, but it's not 50% efficient, it's more than that. I'm not trying to "convince otherwise", I'm just stating that your estimate of "double the time to charge" is incorrect.

          • Tim242

            I tried the Nexus 4 out for a week. It took 5 hours to charge wirelessly,vs 2.5 wired. I was using the LG wireless charger. I would think that all Qi chargers are equal, but not sure.

          • Justin W

            I was using the Nexus Orb (I used the same cord for both tests, the one that came with the Orb).

          • dextersgenius

            I always wanted to buy the Orb but I've heard of reports that the surface looses it's grip after a while, causing the phone to slip and fall? Also, does the charging efficiency decrease a lot if you use a TPU case?

          • Justin W

            It does lose it's grip, but typically it's because of dust settling on the surface. If you wipe it off with a dry cloth (one that doesn't leave lint, like a shop rag or the like), it should remain fairly grippy.

        • Matt V

          True, there are some losses associated with wireless charging, though we're taking about ~2 watt hours per full charge. To put this in perspective; if you accidentally leave a 100 watt lamp on for an hour, you just wasted 100 watt hours which costs about $.01. I propose these miniscule losses are much less costly than having your phone connector wear out, and having to replace or repair your handset. Just some food for thought. :)

  • xHabeasCorpusx

    I can confirm this to be an issue with:

    Nexus 7 2013
    Droid DNA 4.3 AOSP and the HTC One Sense
    Nexus 4

  • http://www.jonbross.com/ Jon Bross

    Woo! Thanks for featuring this, guys! Hopefully the more exposure this issue gets (as well as other 4.3 major bugs) the faster and more likely it is that Google will push a bug fix update.

    P. S. Thanks for the shout out!

  • Ryan Stewart

    I'm glad I don't have this yet because I love my wireless charging.

  • Michael W.

    I had a similar issue with 4.2.2 on my Nexus 4. I would put mine on the wireless charger (or use the cable) and the screen would not come on after I took it off the charger. It was very annoying as it was totally random when it did it. My wife's nexus 4 was the same way. I don't remember the exact post but someone on XDA figured it out. They posted this app in google play

    https://play.google.com/store/apps/details?id=com.sash.sodeliminator

    That app is AMAZING! It fixed my wakelock issues 100% and they have never been back since. My screen turns on just fine no matter what and my battery life is roughly 2 days all the time. GET THAT APP!!!!

  • Michael W.
  • Thomas Cai Jinzhan

    I have the N4 and used the wireless orb to charge as well. I am also using bettterbatterystats....can you enlighten which wakelock in question is the one that is causing this? I might need to take a look on it myself.

  • anezarati

    glad to know about this. i always wondered why my phone lasted a little less when i charged via wireless orb vs the cord.

  • anezarati

    do you have to be rooted to use BetterBatteryStats? i cant really find anything on the app page, but it seems like you have to be.

    • Russ

      No

  • Vito

    This is why I stopped used the wireless orb...

  • Rodalpho

    Note that this exact same issue also occurs on the 2013 nexus 7 tablet.

    It effectively renders wireless charging unusable.

    Confirmed as not fixed in JSS15Q.

    • Pam Griffith Miles

      Tks!?

  • Rodalpho

    This is not fixed in JSS15R.

  • Wolf Baginski

    While I am not sure that it is the same problem, since my Nexus 7 upgraded to Android 4.3 it has switched on from sleep mode every time I connect or disconnect the power.

  • Roddisq

    My Galaxy S3 Wireless charging started acting up after upgrade to 4.3. When you place on the mat to charge exactly 50% of the times does not trigger the charging process. It is exactly 50% like when you place the first time it charges, then you remove it and place again it does not then you remove it and place again, it does charge, and keep this loop forever.
    The curious thing is that when you place it on the mat and just unplug the power supply from the wall, it triggers charge every single time...You may say that Im not placing it correctly on the mat, but I have done it many, many times to prove it and my theory is so far correct. Anyone has experience this?

  • Pam Griffith Miles

    What about the Nexus 7......???

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