1. AC Question's Avatar
    The last several times when I've gotten the battery low alert and I've plugged it into the white brick charger, my tablet powers off. This only happens when I plug it in after getting the alert: if I plug it in before getting the alert, it charges and goes on about its merry way.

    When it shuts down, it'll show a "drained" battery icon with a little "loading" circle. After about 30 seconds (during which the tablet is completely unresponsive), it'll show 20% or so in the battery icon. At that point, I can boot. When it finishes booting, there are several things of note:
    1. The battery is usually at 25% or higher.
    2. The wifi connection will not reconnect without manually turning wifi off and back on again.
    3. Sometimes (not all the time), the clock has been reset to midnight on 1/1/2008. This breaks the ability to use most apps until you reset the clock (the S3 can only be manually reset, unlike the S4 which can synchronize online).

    Anyone else run into this?
    04-16-2015 08:46 PM
  2. Golfdriver97's Avatar
    Welcome to the forums. You might have a battery showing it's age. Have you tried a different one?
    04-16-2015 09:31 PM
  3. Rukbat's Avatar
    1) You're asking for a short battery life. Never let the battery drain down to less than 40% (50% is the ideal charge point). See The Care and Feeding of Lithium Polymer Batteries.

    2) The phone is shutting off at 20%. Since the calculation of State of Charge is inaccurate when the charger is plugged in, it's being conservative (trying not to destroy the battery) and shutting the phone off when you plug the charger in (because that 25% indication the computer is seeing could be 19% or less).

    3) The battery will show a higher percentage with the charger plugged in that it's actually at. (That's because the only practical way to measure the SoC isn't accurate with a charger connected.)

    4) You probably have Wifi set to power save (that's the default - you can change it in the Service Mode menu (dial *#0011#, press the menu key and go to WiFi), but it'll cost you battery. It's off when the battery is way down, so it stays that way (even though the indicator shows that it's on - the "on-off" signal is "on", but the power to the radio is off.)

    5) The clock isn't accurate if the battery drops too low - no electronics is guaranteed at voltages too low to work. (Which is why hard drive heads are pulled away from the disks at power off - the computer can write garbage to the drive as the power falls to zero.)
    04-16-2015 10:44 PM
  4. kestrana's Avatar
    (I submitted the question anonymously last night, sorry...)

    The tablet is right about a year old. I typically keep it plugged in overnight, unplug it in the morning, and plug it back in at night; my usage is usually pretty minimal, so it rarely drops below 60% before I plug it back in. Once or maybe twice a month, I'll have it off in another part of the house, using it for something, and that's when the battery gets low.

    I'm reasonably sure the device isn't "just shutting off" at 20% because the last time I got the battery low warning, I didn't put it on the charger right away after I got the message and it stayed on until I plugged it in at 9% (I was right in the middle of something and couldn't get it plugged in right away when thd message came up). That time, it did NOT power off when I plugged it in. Also, there is a second warning that comes up at 10%...why would that exist if the device just shuts down at 20%?

    It seems to only happen when I plug it in immediately after getting the popup warning.

    Okay, I get that the battery % might not be accurate when the charger is plugged in, but the warning popup comes up at 20%, and another one comes up at 10%. So it's not out of line for it to register at 25% after charging for a couple minutes in a powered off state when I plug it in after the first warning.

    #4 - This is a tablet, not a phone...no dialing. I assume you mean there's something in the settings to control the wifi behavior on reboot (although a perusal of Settings doesn't reveal anything like what you've described here).

    The clock has only reset once in conjunction with the shut-down-on-plug-in, not every time, so I'm not 100% sure it's related. The clock did reset once before when the tablet randomly rebooted itself for no apparent reason while on the charger at 100% battery...
    04-17-2015 06:35 AM

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