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Android battery status not accurate

Discussion in 'Android Lounge' started by pilzdad, Jan 11, 2012.

  1. pilzdad

    pilzdad Lurker
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    I have a question regarding my Samsung galaxy s2 skyrocket. When I plug the phone in to charge it and it reads at 100% when I remove the charger, the phone, no matter how much usage displays 100% battery power. Only by rebooting will it show me an accurate charge amount of whats left on the battery. I tried a few battery widgets and am currently using battery solo widget and it reacts the same way as what the default samsung is.

    Any help or ideas?
     

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  2. EarlyMon

    EarlyMon The PearlyMon
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    Welcome to the forums!

    As a safety feature, the phone runs from the battery while on the charger. The phone battery will never trickle charge.

    So, what happens is this - when the phone reaches full charge, the green light (most phones) come on and the battery shows 100% - and it stops charging. Then, servicing whatever functions are being used in background (or foreground if you're using your phone while on the charger), the battery is used and starts to discharge until it's at the manufacturer's set point, anywhere from 92 to 96%, and then begins charging again.

    If you graphed it over time, it would look like a long roller coaster of battery power going at the low from the 90s to the top at 100% - it would look pretty much like a sine wave.

    When you pull your phone from the charger, it will say 100% but it will really be anywhere along that curve from the 90s to 100%. Only after running normally for maybe 15 minutes (or rebooting) will the true battery percentage show.

    This is identical to how laptops charge and operate - it's the same safety technology.

    In the laptop world, this leads to snake-oil sales to replace perfectly good batteries, in the phone world, this leads to no end of phoney battery tweaks. You'll think you're using up to 8% of your battery in 15 or 20 minutes or that something is broken in the read-out - when it's just the design.

    If you pull your phone off the charger the instant it turns green, you'll find it consistently showing 99~100% charge.

    The actual percentages are calculated by process taking a sensor reading of the battery's mV state and comparing that to a battery calibration file, and then calculating percentage. That same calibration file is slowly updated over time as the system continuously learns about the actual battery installed.

    For that reason, new phones seem to get longer life within the first few weeks to a month of use. It's simply the calibration file getting - well - calibrated.

    The benign battery tweaks simply force that calibration to occur more quickly, but really isn't a problem if you skip that.

    If you root your phone and replace the software, you can get a really screwed up battery calibration file, so rooter use a calibration tool to erase the file so it can be rebuilt properly over a short time's worth of use.

    Otherwise, avoid things like tips telling you to drain the battery completely several times before use. Usually that sort of forced use can be accompanied by a rapid heat build-up and heat is not a battery's friend.

    That's the whole story - hope this helps! :)
     
  3. pilzdad

    pilzdad Lurker
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    But I find that when I remove the phone from the charger after several hours of use, it still reads 100%. When rebooting the phone, it than drops to 50-60 or whatever percent its at and performs normally.

    Are you saying that after time it will fix itself?

    thanks for the response!
     
  4. jerofld

    jerofld Fixing stuff is not easy
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    Over there <points>
    The short story is: If you mean that the battery doesn't report much of a change until it's below 90%, then that can be normal (depending on hardware configuration and usage).

    If you mean that after an hour of medium-heavy use, it still shows 100%, you reboot, and you see 60%. Then that could be an indicator for either a bad battery meter or your battery stats file is corrupted. If you're rooted, you can reset the battery stats and see if that fixes it. If you're not rooted, you need to do a factory reset. If resetting the battery stats doesn't fix it, I'd recommend you return it to a repair center to get checked out.
     
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  5. pilzdad

    pilzdad Lurker
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    That is definately what its doing. I know google backs up all of my contacts, calendars etc, but is there anything else that stores apps and settings?
     
  6. EarlyMon

    EarlyMon The PearlyMon
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    Not really with the stock setup. For an unrooted user, your best peace of mind is to go with MyBackup Pro, get all of that onto your SD card, then copy the whole SD card to your PC by select all and drag and drop. I make a folder under my documents called SD-backup and that makes it easier.

    Also - double-check by logging into Gmail on the web that all your contacts really are on the Google cloud. My motto, if one thing is broken, don't trust anything without double-checking first.

    Let us know what you find!!
     
  7. jerofld

    jerofld Fixing stuff is not easy
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    Without rooting, not really. Google will also restore apps, if you elect for your phone to do that, but all the settings will be reset to defaults.

    Alternative markets, like AppBrain, can save app lists and re-download them to your phone, too.
     

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