08-30-2014 06:55 AM
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  1. Clad14's Avatar
    Judging by the alarming number of threads related to battery life with DP 8.1 or Cyan, I decided to create this thread to try to get better understanding of battery management issues with WP 8.1.

    Of course, I want everyone to realize that not everybody has battery life issues with his/her Windows phone. As usual, those who are satisfied have no reason to post about it and so, people with battery life concerns are over-represented. Personally, I recently got a used Lumia 925 and updated to DP 8.1 immediately and I am totally satisfied with my battery life. However, I am holding up on Update 1 since bugs have been reported. Don't need Update 1 features anyway. I charge my phone via usb cable or more recently via a Nokia Qi wireless charging station and switch it to airplane mode at night because Windows phones cannot be turned off while charging (Q1). In the morning, it indicates 100% state of charge. Many users have reported non 100% reading in the morning, which I consider a major issue (Q2).

    Nevertheless, I have genuine interest in battery technology and decided it would be useful to try to gather every piece of information about battery management in WP OS.

    Tips

    People with battery life issues running any version of WP 8.1 should pay close attention to the OEM Battery Saver app. This app shows you which apps are draining the more energy from your battery and allows you to remove permissions for background processes on an app-by-app basis. Under the "usage" tab, you'll see a list of all apps that drained energy since your last charge (I believe) and what part of it came from the background processes of the app. This foreground Vs. background break out can be very useful. For instance, I can see that the game "Total Conquest" drained some juice even though I never played with it. It was the background processes associated with this game. Unfortunately, Battery Saver only displays a bar which, I guess, refers to the points (%) of the battery capacity that were consumed but there is no numeric display. I imagine a full horizontal bar means that this particular app drained 100% of the battery capacity? Anybody wants to play some 3D game in airplane mode from full charge to fully depleted for confirmation?

    Stay tuned!
    Rasmus Klingenberg likes this.
    08-13-2014 11:13 PM
  2. Clad14's Avatar
    Q&A section:

    Q1. Why can't I turn my phone off while charging?
    Whether you try to power your device off while plugged in or plug in a powered-off device, you will notice that the device remains/turns on.
    According to my reading, it is because the management of the battery is assumed directly by the WP OS with Windows phones. Therefore, charging can only occur with the OS booted up.
    This is different from most other devices where a dedicated smart battery management IC (integrated circuit) is installed on the phone PCB (printed circuit board) and handles the charge control and safety features associated with the battery. Such an IC has the ability to communicate directly with a "smart" power source and does not need any OS involvement for managing the battery. It keeps managing the battery even with the phone turned off. This IC can also communicate with the OS for reporting the current state of charge and other operating variables such as voltage, current, temperature, ... The OS (iOS, Android) can then display this state of charge information on the device screen.

    Q2. Why isn't my device reading 100% charge in the morning?
    Here, we have two plausible scenarios. On the one hand, it could be that the phone reaches full charge in the middle of the night and then decides to switch charging off as per Lithium-ion charging protocol standards. But then, some background processes and/or connectivity features can drain some of the stored energy. Proper charge management would result into a resumed charging to bring the phone back to 100% as soon as it drops below, let's say, 97%. This does not seem to be happening.
    On the other hand, this could be an issue with the calibration of the battery management algorithm. Indeed, each battery design (understand Lumia 920 Vs. 1520 Vs. 520) has a specific open circuit (i.e. idle) voltage (OCV) to state of charge (SOC) relationship. This means that WP OS should be able to recognize the device model and adjust its OCV Vs. SOC relationship in order to report accurate charge level. Provided the OS is fed with relevant information, it shouldn't be a problem with a new device (fresh battery). However, problems arise when battery ages and degrades. Most degradation processes alter the OCV Vs. SOC relationship and thus, user will experiment inaccuracies and discrepancies with the readings of the charge level. I will develop on that topic later on but let's focus on a simple example for now.
    Let's say that, once fully charged, your fresh battery presents an open circuit voltage (or idle phone for couple of hours, close enough) of 4.18V. The OS knows to report 100% when it reads 4.18V across the battery. Few months later, the same battery, not so fresh anymore, now presents an OCV of 4.12V after full charge. The OS was initially told to report 90% when reading this value. Granted the OCV Vs. SOC relationship has not been updated in the meantime by means of intelligent recalibration, your phone will now display 90% state of charge when you wake up, even though it might actually be charged to its fullest capacity.
    There's no way to tell for now because the WP API will only let you access the state of charge reading. Quantities such as voltage, current or temperature are not publicly disclosed.
    For the same reason, you might be experiencing sudden drops where the battery appears to lose a handful of charge within a few instants. This could be another symptom of OCV Vs. SOC miscalibration.

    Q3. LTE, 3G or Wifi?
    According to this article by Huang et al., and based on their usage scenario, LTE is the least energy efficient protocol, then comes 3G while Wifi offers the best energy efficiency. Under the test scenario, LTE consumed 5 to 12 times more than Wifi and 3G 5 to 8 times more.
    Also, uplink on cellular network consumes much more energy because your signal has to reach a distant tower. There is a comparison of uplink/downlink power consumption for the 3 technologies in this article (figure 9). The conclusion to this is that you should refrain from uploading data to the "cloud" while on 3G/LTE connectivity.
    I read somewhere that turning Wifi is bad because with cellular already on, that means you now have two power hungry processes. This is a wrong interpretation of how communications work. Power consumption rises up only during transmission, while idling is designed to be energy efficient (figure 3). Therefore, using Wifi to transmit data should save you energy even though cellular is on at the same time.
    Remember that your local network coverage can significantly alter these results. Poor Wifi might result in increased power consumption and cellular data might then become more interesting.
    Last edited by Clad14; 08-21-2014 at 01:36 PM.
    08-13-2014 11:15 PM
  3. charlienk's Avatar
    1520 8.1 here. Based on my readings, battery issue resides in facebook apps. This being facebook, instagram, and most of all facebook messenger.

    Without the apps installed, by 5pm, I average a 52% with the apps installed and not open, I come home at 32%. Try it yourself, see the results.
    08-13-2014 11:19 PM
  4. grininja's Avatar
    I had 8.1 DP on Lumia 720. After Cyan became available I went back to 8.0 (with Nokia Software Recovery Tool) then I updated to 8.1. No Develeoper Preview yet.

    Now the battery drains fast... faster. Best example:
    Before (WP8.1, DP, Black): going to bed with 98%, in the morning went to 96%. This is normal, 2% overnight.
    After (WP8.1, Cyan): going to bed with 98%, in the morning went to 76%. This is insane, over 20% on idle!

    I installed the apps I used to have before, similar settings... I only have whatsapp for social apps. No facebook or facebook messenger, no instagram...
    Usage settings in Battery Saver hub shows nothing special. All seems ok. I'm thinking of hard-reseting. Again.
    belodion likes this.
    08-14-2014 02:51 AM
  5. grininja's Avatar
    ...
    08-14-2014 02:53 PM
  6. Misha Zinoviev's Avatar
    Do someone know how much energy drains GPS unit ? Like if I want to use Cortana, or WiFi management?
    08-14-2014 03:14 PM
  7. ksmx's Avatar
    I have noticed that oem 'power saver' application is not entirely shutting down wi-fi and gprs connections. When disabled manually, battery drain is similar to WP8 with power saving mode on. What is more, it seems that live tiles are running even during locked screen, even those which are purely off-line. Simply speaking, the more animated tiles you have, the shorter battery life of your device is. These bugs were present in all developer versions of WP 8.1. I am surprised they do exist in official nokia 'cyan' update. Tested on L820, L920 and L925.
    belodion likes this.
    08-17-2014 08:10 AM
  8. belodion's Avatar
    grininja: my battery usage experience similar to yours.

    Posted via Windows Phone Central App
    08-17-2014 08:50 AM
  9. belodion's Avatar
    ksmx: I wondered why they say more tiles on start screen uses more battery...you wouldn't think so when phone is off but if you're right that's interesting. Had already stripped some out, now I'll remove more. Thx.

    Posted via Windows Phone Central App
    Theo_andravida likes this.
    08-17-2014 08:53 AM
  10. Thisis_ugo's Avatar
    Nice thread;)
    08-17-2014 10:26 AM
  11. ksmx's Avatar
    Just check this out Belodion. This observation is not supported by detailed measurements ;)
    belodion likes this.
    08-17-2014 11:19 AM
  12. Clad14's Avatar
    This weekend I played around with an old Android handset of mine (ZTE Blade running 2.3.4).
    I put an app together that logs the battery voltage and reported state of charge (SOC) every minute into a TXT file that I can process afterwards.

    For you to get a sense of how bad battery SOC tracking algorithm can be, have a look at the graphs below. The app is using the screen to execute a controlled constant power charge and discharge. Phone is only running this app and is in airplane mode. Therefore, the SOC evolution should be a fairly straight line, which it is not...

    My long term goal is to build a similar app for WP but I can't read the voltage with the public methods in WP8. I opened a thread on XDA to find a way around it.

    charge.jpg
    discharge.jpg
    Last edited by Clad14; 08-21-2014 at 01:34 PM.
    08-18-2014 01:35 PM
  13. Branden Lucero's Avatar
    my L520 used to get a battery life of around 24-25 days on standby before the update. now i'm barely lucky if i can get maybe 3-5 days. SOMETHING is draining this phone rapidly after the update. i checked battery saver and app usage, and everything is "not allowed" as best as possible. the only thing installed on this phone are games. there are no social apps, no facebook, no instragram, etc. i only use this phone for xbox gaming and music.

    all my apps are installed to the SD card <-- therefore, i believe this is what may be causing my phone to drain rapidly, as it has to access the card to use my apps.

    eveything is turned off. location is off. bluetooth is off. wifi is ONLY on, when i need to access the store or go online for xbox. battery saver is set to "always". its set completely on Airplane mode. its even on the lowest brightness. and yet, still rapidly draining... there is no sim card, so there isnt even cell service on this phone. hell, i dont even browse the internet on this phone. THAT is how clean i keep it.
    08-18-2014 01:47 PM
  14. Clad14's Avatar
    my L520 used to get a battery life of around 24-25 days on standby before the update. now i'm barely lucky if i can get maybe 3-5 days.
    I believe your phone was reporting 24 days but unless you actually verified it by not plugging in your phone in 20+ days, it might simply have been an erroneous claim the whole time. You can't trust the indicator and base your reasoning on it.
    Plus, which update are you referring to, DP8.1 or Cyan ?
    08-18-2014 02:10 PM
  15. Branden Lucero's Avatar
    I believe your phone was reporting 24 days but unless you actually verified it by not plugging in your phone in 20+ days, it might simply have been an erroneous claim the whole time. You can't trust the indicator and base your reasoning on it.
    Plus, which update are you referring to, DP8.1 or Cyan ?
    nope, i can confirm this. i let the phone before update, fully charged. and it ran for 12 straight days all the way up to 50%, it fell to 10% after because for some reason, the screen forgot to turn itself off. so yes, for another 50% and assume another 12 days? yeah, i can confirm its pretty damn accurate for stand by.

    and i was talking about Cyan.
    08-18-2014 03:11 PM
  16. Branden Lucero's Avatar
    here's a picture of the battery life i was able to get, before i updated. i'm glad i took this experiment when i did!

    also keep in mind, before the update, i had at least 20 titles (small form) on the start screen, so i dont think tile count had anything to do with it.

    http://i140.photobucket.com/albums/r...ps76b7d6cb.jpg
    08-18-2014 03:35 PM
  17. Clad14's Avatar
    That's interesting. I have a spare 520 too. I'll see if I can get similar figures.
    08-18-2014 03:51 PM
  18. grininja's Avatar
    there is no sim card, so there isnt even cell service on this phone. hell, i dont even browse the internet on this phone. THAT is how clean i keep it.
    Then what are you using your phone for?
    It is interesting what you're saying but it is kind of irrelevant because obvious reasons.
    08-19-2014 01:26 AM
  19. ksmx's Avatar
    Currently my L925 shows 2% discharge/day using battery saver and disabled wi-fi/data. With enabled wi-fi/data it shows 5% per hour.
    08-19-2014 02:28 AM
  20. Branden Lucero's Avatar
    Then what are you using your phone for?
    It is interesting what you're saying but it is kind of irrelevant because obvious reasons.
    i use it for xbox gaming and music. its my personal media phone. my recreational phone. the only thing that battery saver says its using the most is that Lock Screen Beta, which i'm thinkin' about removing, to see if that's what's causing my battery drain. somewhere, i've read a user say something about the live tiles never going to sleep when the phone sleeps, but i dont know if this is directly related to this screen lock app, but i'm gonna find out. i head to Denver tomorrow, so i'm going to uninstall the app, and fully charge and see how it goes.
    08-19-2014 03:05 AM
  21. belodion's Avatar
    Just check this out Belodion. This observation is not supported by detailed measurements ;)
    Well I've removed a load of them now, for example a lot of the many many photography apps which I realised I never used. I may put some back because I think my battery problem is now fixed. I've posted about it elsewhere but will repeat here. After a soft reset I noticed three app updates had been trying for a week to download. I'd received no notification of this in the App Store tile. During this time, battery usage graph showed many small downward steps, presumably caused by updates repeatedly trying to download. I downloaded them manually and now the battery usage graph descends in a smooth line. Consumption seems back to normal. The soft reset may have had a beneficial effect as well.

    Posted via Windows Phone Central App
    ksmx likes this.
    08-19-2014 02:53 PM
  22. Theo_andravida's Avatar
    If there are a lot of apps and games on our phone , more than 50, and 30 tiles on start screen, I can be reason for battery draining fast???
    08-19-2014 03:28 PM
  23. belodion's Avatar
    ^^^Microsoft themselves say that the more tiles on the start screen, the higher the battery consumption. What isn't clear is whether that is true even if the phone is switched off.
    The more apps you have, even if you hardly use them, the higher the battery consumption if only because some will run in the background.
    Well that's how I see it but I stand ready to be corrected.

    Posted via Windows Phone Central App
    08-19-2014 05:12 PM
  24. s2mikey's Avatar
    ^^^Microsoft themselves say that the more tiles on the start screen, the higher the battery consumption. What isn't clear is whether that is true even if the phone is switched off.
    The more apps you have, even if you hardly use them, the higher the battery consumption if only because some will run in the background.
    Well that's how I see it but I stand ready to be corrected.

    Posted via Windows Phone Central App
    This makes sense. I have therefore removed any unused tiles from my main screen. Overall, battery life for me has been excellent on my 520 with 8.1 but I am NOT a power user or a regular gamer. I can probably get 2-3 days out of a charge at my usage rate. :)
    belodion likes this.
    08-19-2014 07:12 PM
  25. Branden Lucero's Avatar
    uinstalled Live Lock Screen Beta, went into the Notification Center and tweaked it to shut off everything from being notified. let it charge over night. took it with me to Denver, came home. 15 hours later of checking it, BAM.... 100% battery still. oh yeah, i'm a genius baby.
    belodion likes this.
    08-20-2014 12:13 AM
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