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Power 20% to 0% instantly

Discussion in 'Android Devices' started by Melvster, Apr 19, 2012.

  1. Melvster

    Melvster Lurker
    Thread Starter

    Hi guys, I have what i believe to be an entirely unique problem!
    When my phone is fully charged it will discharge down to about 20% sometimes 15% then it will turn off instantly without warning.
    Now if i start to charge the phone again and unplug it when it gets to say 20% it will give me 20% of power. Ie. i will get the 15% 10% and 5% warnings.
    I have checked with the power usage graph and it shows gradual decline to 20% then *bam straight to 0%.
    I have just noticed that when i fully charge the phone, while it is on, the graph steadily increases to 80% then goes direct to fully charged.
    I have just preformed a battery calibration, Ie. fully charge while powered on unplug power off charge to full, power on charge again and it still doesn't work.
    It is also not a problem with the battery as i have 2, both HTC branded, with the same results.
    The problem initial happened while on Froyo and i recently updated to Gingerbread via the HTC website and it hasn't fixed it.
    Any ideas? I suspect the phone is somehow preventing the battery from fully charging and then misrepresenting the charge available.
    Thanks for any help.

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  2. SUroot

    SUroot Extreme Android User

    The 20% to 0% is certainly nothing new. That's the true usable capacity. Li-on batteries need protection from running down. All desires shut down at around 15% or so.

    However, the problem is that that 15% should register as 0%.

    If you see it shut down at 15-20%, if you boot it up immediately (may need a little power to do so) it will read at 0% - which is what it should have read as.

    So the fact that it shows fully charged at 80%, although I've never witnessed this - actually comes as no surprise to me. That 80% is actually the true usable capacity of the battery. The battery stops charging when it hits the battery's capacity in millivolts.

    In short, you are not losing anything. You are using the full 100% usable capacity of your battery, however only around 80-85% of the battery is usable. Your software is seeing the entire battery as 100% where it should only see the 80-85% as 100%.

    I hope that at least helps some way towards understanding.

    Now is it possible to truly calibrate the battery to show 15-20% left as 0%? Yes, however this requires a very specific kernel which requires being rooted. There may be other ways, but I've not tried any.
  3. davo26

    davo26 Android Enthusiast

    ive also got this problem with my wifes desire, altho slightly worse, it dies at around 35%. as you say, when its switched back on it shows 0%.

    my wifes desire IS rooted tho, so could you let me know how i can at least get it to show the correct %age please? which kernel do i need? at present shes got manu1.4 or something i think.

    one other thing, it dies mid-afternoon on light usage, so is it about dead anyway? its only around 20 months old :-/

  4. SUroot

    SUroot Extreme Android User

  5. davo26

    davo26 Android Enthusiast

    thanks, already got that kernel, so running the app now. bit confusing, thought i was doing it wrong having to keep putting those different values in, and also a bit unsure about how ill know when its charged, as it says to LYPTFA, which means screen will obviously be off, so cant see when the CHGTF flags lit.

    but...... ill just follow instructions and see how it goes. possibly leave it charging all night.

  6. davo26

    davo26 Android Enthusiast

    ok, not too sure whether thats gone ok or made things worse to be honest.
    it was all a bit strange really, but made me hopeful that it was improving matters, as, during the calibration, it would reach 15%, then down to 10%, then shoot up to 18%. it did this a couple of times, so i was hopeful i was 'discovering' new juice that was being ignored in the past. all the time i was watching the voltage didnt reach 3201 and it did indeed seem to be going down slowly.

    one hiccup was that on about 10% i left it for a few mins (voltage didnt show any signs of reaching that figure yet) but when i came back the phone was dead!! grrrr..... i was so annoyed id missed the 'plug it in NOW' message.

    had no alternative but to start charging again and hope for the best. and again, something happened to give me hope. firstly, i switched it straight back on, it showed 0% and died. i charged it for about 10 mins, then unplugged. it showed 30%, then as i was repeating the early steps, it was taking its time dying, so again i thought i was discovering new juice that would be mine all mine when it was recalibrated :)

    all went ok this time, plugged it in when it said and left for 5hrs to charge in airplane mode. switched off and rebooted this morning, phone started at 100%.

    however, after 10 mins on facebook, phone was showing 94% :-( half hour later it was 90%. its not looking good. battery may be dead by dinner :-/

    anyone know this software and whether theres anything else i can try?

  7. SUroot

    SUroot Extreme Android User

    Well OK, youi have to keep the screen awake and the phone in your hand whilst its deing. This can take 5 minutes or so. When it says plug it in, plug it in. Your radio at this point is still off (leave it off) and let it charge. Thats all.

    Yes it does appear to shoot to 30% when learn mode is enabled.. Mine does that too.

    I would say calibrate again.

    10mins facebook, 6%. Yep thats about right. Although if you're hoping for us to spot anomolies, we cant without knowing screen brightness, screen on time, and screen % from the battery info screen.
  8. davo26

    davo26 Android Enthusiast

    ok ill do that. just one thing that i dont understand about your answer. you said i have to keep screen awake and phone in my hand for 5 mins whilst its dying. thats sort of what i was expecting to have to do. i thought the software would drain the battery quickly whilst i waited. however, it was a couple of hours or so. and probably took longer because i was in airplane mode.
    have i missed something out?

  9. SUroot

    SUroot Extreme Android User

    maybe your battery is so far off the true value that it shuts down far too early. Watch the mV section and match it to where it should die as according to the guide.
  10. davo26

    davo26 Android Enthusiast

    do you mean the 3201 figure? it should hit that then die? what if it doesnt? it would still just calibrate it anyway wouldnt it and nothing i could do to change it?

  11. SUroot

    SUroot Extreme Android User

    It will. That is when the battery cuts off, regardless of what the software tells it.

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