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  1. pmouse's Avatar
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       #1  
    I have two Lumia 920s, one black, one red for my GF. Both are charged by the wireless charger, both are running AT&T LTE with similar apps installed. I charge them daily overnight, practically at the same time.

    On the black lumia, after a day of light usage (pretty much all emails), the battery would have >80% remaining, and the "estimate remaining time" would show something like 2 days.
    On the red one, it'll come home with 40% remaining, and if I don't charge it immediately, it'll run out of battery in 2 hours. I also notice that simply putting the phone of the desk without ANY usage, it'll warm up near the top of the phone, indicating some sort of power drain.

    Yesterday I've decided to get to the bottom of this. So I begun with the red lumia at 40% power, turn on airplane mode, kill all background apps (at that time, only Weather Channel and Evernote), and just let the phone sit for 2 hours. After which I came back and found the phone still at 40% and with a cool back. This tells me that one of the action I took eliminated the power drain. So I begun turning things on one by one (only keep one potential source on), then wait for an hour and see what happens.

    I've tried Bluetooth, NFC, WIFI, Cell with no data, and cell with data. Interestingly, when I left turned the cell radio on, the phone shows the most significant drain in that hour. This is with no background task running, and no LTE data connection - ONLY the phone radio is on.

    I was really lead to believe that the red unit is defective, and was going to return it. Out of curiosity I power cycled the device (Vol Down and Power together for 10s) just to see what happens. Strangely, after the device reboots, I can no longer reproduce the drainage. Today I turned everything back on, and after 7 hours of light usage (web and email only), it's showing 95% battery left. The estimate time remaining is...7 DAYS 10 HOURS ?!?

    So needless to say I won't be returning it anymore. This left me wondering was it the soft reset that cured the problem, or was it something else? I won't be able to find out myself as it no longer repros for me. I hope someone else on this forum that has similar problems can try this method and report back what your findings are. The thing to try are basically:

    1. identify the source of your battery drain by turning on airplane mode, and kill all background tasks
    2. soft reset by holding vol down + power button. Note: your data and settings will remain, this is only rebooting phone.


    Update 11/19:

    Today on the red lumia the same problem occurred again. By the time I went home the battery had only 50% left, and the estimate time shows 3 hours. Again the phone would be warm even in standby, so I've powered it off, and restarted. Now it's got 30% of battery and 14 hours of estimated time - so resetting the phone does cure the drain.

    This leaves me to believe that there are some app/background task/os task that was not properly shutoff. I'm thinking either Weather Channel or Bluetooth pairing with car radio. Tomorrow I'm going to run it with bluetooth completely shutoff, and see if the program persists.

    Just a side note: the phone, when in standby, gets warm near the top left corner. Anybody know what's in that corner?
    Last edited by pmouse; 11-19-2012 at 10:52 PM.
  2. Ali Babba's Avatar
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    150 Posts
    #2  
    I think it's a firmware/OS bug. I've done a factory restore only to see my percentage remaining and estimated battery life swing anywhere from 6 hrs on 90% charge, to 4 days on the same charge, on the same day. This is with all NFC/BT/WiFi off as well as uninstalling most apps. I've also seen the percentage go from back up (ie: 80%, then 5 min later its at 85%). Then after re-installing and restoring everything I use, I still see the same erratic behavior. I really hope MS fixes this soon.
  3. potahov's Avatar
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    13 Posts
    #3  
    just soft reset seems to be enough to fix this temporary, no need in factory reset
    mine died in few hours once and turned off itself - after this it works just fine with battery
  4. pmouse's Avatar
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       #4  
    Update:

    Today on the red lumia the same problem occurred again. By the time I went home the battery had only 50% left, and the estimate time shows 3 hours. Again the phone would be warm even in standby, so I've powered it off, and restarted. Now it's got 30% of battery and 14 hours of estimated time - so resetting the phone does cure the drain.

    This leaves me to believe that there are some app/background task/os task that was not properly shutoff. I'm thinking either Weather Channel or Bluetooth pairing with car radio. Tomorrow I'm going to run it with bluetooth completely shutoff, and see if the program persists.

    Just a side note: the phone, when in standby, gets warm near the top left corner. Anybody know what's in that corner?
  5. Frantics's Avatar
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    28 Posts
    #5  
    This mysterious drain happened to me today too. You're right it seems like an invisible process is getting stuck in the background causing massive heat and drain.

    It happened to me while I was transitioning between LTE and Wi-Fi. My 920 is a fresh replacement with virtually no apps and zero background tasks and it was getting relatively great battery life (for the most part) prior to this.

    Upon entering my Wi-Fi area, I turned off LTE data, turned and Wi-Fi and tried checking the People Hub but the hub won't refresh because the phone can't connect to the access point. So I toggled WiFi and it connected. After the People Hub refreshed, I closed out of all tabs and I laid the phone down on my desk. An hour later, I noticed the phone got hot and we all know what that means... battery drain. Surely enough, it devoured close to 40% in an hour! And yes, it took a soft reset to stop the drain.

    Oh, and I remember this happening two days ago too while moving from LTE to Wi-Fi. I thought it might be the WPCentral (which I uninstalled) but since it happened again today, it's definitely looking more like something within the OS is going awry.
  6. pmouse's Avatar
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    17 Posts
       #6  
    Quote Originally Posted by Frantics View Post
    This mysterious drain happened to me today too. You're right it seems like an invisible process is getting stuck in the background causing massive heat and drain.

    It happened to me while I was transitioning between LTE and Wi-Fi. My 920 is a fresh replacement with virtually no apps and zero background tasks and it was getting relatively great battery life (for the most part) prior to this.

    Upon entering my Wi-Fi area, I turned off LTE data, turned and Wi-Fi and tried checking the People Hub but the hub won't refresh because the phone can't connect to the access point. So I toggled WiFi and it connected. After the People Hub refreshed, I closed out of all tabs and I laid the phone down on my desk. An hour later, I noticed the phone got hot and we all know what that means... battery drain. Surely enough, it devoured close to 40% in an hour! And yes, it took a soft reset to stop the drain.

    Oh, and I remember this happening two days ago too while moving from LTE to Wi-Fi. I thought it might be the WPCentral (which I uninstalled) but since it happened again today, it's definitely looking more like something within the OS is going awry.
    Interesting theory, however, like I said, I have two 920s, one never had any battery problems. I've been playing mirror edge for 2 hours after a day of light usage, and it's still at 50%+. Could the WIFI chip be defective then?

    I practically transition between WIFI and LTE alot daily. I'll test tomorrow with WIFI and BT always off, only LTE, see if the issue goes away.

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