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Battery concern...

Discussion in 'Android Devices' started by Juyeop, May 11, 2011.

  1. Juyeop

    Juyeop Newbie
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    Hi i've been using the nexus s for about a week since i got this from best buy. My concern is that the battery is full-charging to only about 94%~95% now on nexus s.....is it normal to show up that way??? the firmware version is 2.3.4 though but it was happened even in 2.3.3. gimme advices plz~~
     

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  2. frankkduf

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    yeah its normal for this device !
     
  3. bfksc

    bfksc Android Expert
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    No it is not normal. It's a code error (bug) in the Nexus S firmware for the charging process that shuts off the charge current a bit too early. It won't really hurt the battery, but it's certainly not normal and should be corrected to allow 100% charging. Some people erroneously think it's some sort of battery extending technique, but that is incorrect. It's a firmware issue. All current stock Nexus S firmware versions have this bug so it's a common issue among users, but not normal.

    It has been reported to Google and hopefully they produce a fix soon.
     
  4. quantumrand

    quantumrand Android Expert
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    No, it is normal. It does it to protect the battery from overcharging. Traditional chargers will charge a battery up to 100% and then switch over to a trickle charge. For Li-ion batteries, like those in cell phones, the continued inbound currant is actually VERY bad for them and results in a loss of total capacity over time.

    The Nexus S switches to a trickle charge around 96% or so and shuts off the charging circuitry the moment it hits 100%, restarting the trickle when it drops below that 96% level. When it first hits 100%, it displays "Charged" even though it could drop as low as 95% during it's trickle state.

    Because of the way the Nexus S charges, you do miss out on the top 5% of the battery from time to time, but it ultimately extends the life of the battery. When I say "life of the battery," I mean that it doesn't lose as much of its capacity over time. Don't confuse "life of the battery" with "battery life." The Nexus S' charging method sacrifices a bit of battery life when the battery is new in order to keep good battery life when the battery is older.
     
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  5. bfksc

    bfksc Android Expert
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    I'm sorry but that is not correct. All Li-Ion batteries in phones have a microchip that actually monitors current, voltage, temp, discharge rate, etc. That chip is there to cut off the charge current when the battery is full to prevent overcharge, it's a protection circuit - you CAN'T overcharge a Li-Ion in these phones even if the phone malfunctioned and continued to charge at full rate. It's just not possible, unless the chip failed too which is highly unlikely.

    Also, phones don't continue to trickle charge Li-Ion batteries because the chip cuts off the current. What happens once the battery hits ~70% is the current is cut down to about 0.1C to top up the battery to 100%, then the current is cut off completely. If the phone is still plugged into a power supply then the battery isn't used and it will remain at 100% for many days. But even though the phone is getting power via the power supply, the battery will continue to self-discharge very slowly due to electron loss and the tiny drain from the microchip. After a week or so the battery will drop below 90% at which point the phone will top up the battery to 100% again. It will continue this cycle until it's unplugged and used on battery power alone.
    That info is completely wrong and misleads others. I don't know who started this crap about the Nexus S "charging technique", but it's plainly and simply wrong. No phone manufacturer has every used such a poor design to charge the phone's Li-Ion battery. It's counter-productive and does nothing to extend the life cycle of a Li-Ion battery.

    I've been working with rechargeable batteries and cells for 20 years so I know a thing or three about them, and I can say without a doubt that you're just quoting someone else's misinformation about the Nexus S. What I know about Li-Ion and charging circuits is not just idle data. I can assue you, the Nexus S has a bug (or design issue if you will) in it's code and does NOT charge properly (voltage levels are never high enough to achieve a full charge). Do a google search for "xda developers nexus s battery charge bug" and you'll find a thread that I posted in where a developer found the code issue, and confirmed that it doesn't charge fully (intentionally or otherwise)...hang on...ok here's a link to that thread for you:

    FOR NEXUS S - HOW TO GET 100% CHARGE. Found the solution! I hope - Page 2 - xda-developers

    Please have a look...
     
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  6. quantumrand

    quantumrand Android Expert
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    I probably shouldn't have said trickle charging. That's the wrong term. As you said, bfksc, as a Li-ion battery is charged, the closer it gets to full, the lower the current the charging circuitry delivers.

    It's done this way because Li-ion batteries have a very stable discharge voltage. Older rechargeable batteries (like a NiMH AA battery for example) would output 1.5V only briefly when completely charged. By the time it's half full, it would be down to outputting about 1.3V. This made it very easy to measure its charge level based on voltage. Li-ion batteries hold a very steady 4.2V per cell generally from "100%" down to as low as 40%, which means output voltage is a very poor way to measure its charge state.

    To prevent overcharging, the charging circuitry significantly lowers the charging current when the batteries output is at 4.2V per cell. The moment the battery is full, the voltage will drop slightly as the ions saturate around the anode (this is actually bad for the battery but is unavoidable). Once this saturation point is reached, the charging circuitry cuts off the power. Instead of bumping up against that saturation point over and over again, the Nexus S (as well as several other modern devices) lets the charge level float just below it.

    bfksc, you say overcharging a Li-ion battery is impossible because it has special charging circuitry integrated into it. While it's true that it has its own integrated charging circuitry, it is still possible to overcharge it. This circuitry protects against several things, including overcharging, but it cuts out at 4.3V per cell, well over the natural maximum output of lithium cells of 4.2V. It has to allow this higher cutoff otherwise the battery would never charge past 40-70%. Continuing to charge past the 4.2V cutoff causes ions to saturate around the anode and eventually begin to plate around it (known as lithium plating). Once this plating occurs, it is irreversible and lowers total capacity due to the loss of free lithium ions.
     
  7. bfksc

    bfksc Android Expert
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    Yes that's basically right. Once the battery is charged at about 1.0C to roughly 4.10-4.15v, current drops off quickly and the saturation charge tops the battery up to 4.20v or 100%, at which point charging is stopped.
    I don't buy that answer. If the intent was to "fully charge" the battery to 97%, then all they need to do is alter the code to show 100% when the battery is charged as fully as the circuit and code allows. The developer who found this shows the code involved and how it's as simple as changing a few bits of hex to show "100%" in the display.

    And there simply is no reason to not fully charge the battery. This saturation point lasts a few seconds and does not cause any short or long term damage to the battery. If it runs for extended periods, then yes saturation does cause problems. But for the few seconds at full charge, there is no harm in it at all. What harms the battery a LOT more is fully discharging it to the point the phone turns itself off. Many people fully charge and discharge their phones because they still think we need to do that with present devices. So then why didn't Google just code it so the phone shuts off at the ideal low level of 40%? If it's all about extending battery life as you claim, then charging to 95% and discharging to 40% is the perfect way to go.

    So again, why did Google decide to stop the charge at ~96% but not change the code to reflect that new level as 100%? It's like saying don't fill your gas tank when the nozzle kicks back because it's full when it hits that level. Yet you can always get a few more liters of fuel in the tank if you want it completely full without any ill effects.

    If they had simply made ~4.18v the 100% mark, we wouldn't even be having this discussion as everyone would think their Nexus S battery is fully charged and wouldn't give it a second thought. So is this an error? YES it is an error, either the code not charging properly, or their failure to change the code to show 100%. Either way, it's still an error/bug in the firmware that they need to fix.
     
  8. quantumrand

    quantumrand Android Expert
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    I'd assume they did it this way so that it would work with unofficial batteries as well.

    Also, the charging circuitry inside the battery protects against a complete discharge. Using your phone until it runs so low on juice that it turns off isn't that dangerous, though I don't recommend doing it often. What makes it dangerous is if you keep trying to use your phone after it shuts off, or if you take a particularly long time (days to weeks) to plug it in.

    Because the integrated circuitry tries to keep track of the capacity of the battery, it's actually a good thing to remind it by running down the battery every couple months. Just be sure to plug it in immediately after it dies and let it charge fully or you won't get the full benefit.
     
  9. TrIPpY

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    Every battery type has it's own characteristics and should be treated accordingly. I guess it might just make sense that keeping a battery "moving" might be beneficial to keep battery health better for a longer time. By moving i mean: not keeping the battery fully charged all the time.

    This is also what Google stated. Google just might have a point there. From what i know the Nexus S is the first device to implement this charging method and that nobody else does it doesn't mean they're wrong.

    Only the way this is carried out is wrong. There is a weird bug present in Android 2.3.4 like it also was in 2.3.3. When the screen is off during charging, charging stops at 95%. When the screen is on, charging does continue till 100%. I posted a workaround on this forum which works for me:
    http://androidforums.com/nexus-s-su...es-battery-ever-fully-charge.html#post2919937

    See if it works for you.

    ps. i wouldn't want my phone tricking me saying the battery is full while it is not. Better to write down in the manual that charging till 95% full is normal behavior, to lenghten the battery health. And that the battery should be charged a true 100% is definitly the way it should be, in my opinion.
     
  10. bfksc

    bfksc Android Expert
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    Except that Li-Ion actually works best and lasts longer when it is topped up regularly, rather than depleted like Ni-MH.
    Actually they are wrong, and it's NOT a "charging method", it's an error in the coding and charging level.
    As stated before in other threads, and on XDA-developers forums, your charging method does NOT work. It may show 100% briefly, but it's not fully charged as it quickly drops to 96% after just a few minutes even when idle with the screen off:

    FOR NEXUS S - HOW TO GET 100% CHARGE. Found the solution! I hope - xda-developers

    This is an error in the firmware and Google needs to correct it so the battery will be fully charged to 100% as intended. Do not believe anyone who claims that reducing the charge lengthens the battery life as that is incorrect. Li-Ion works best when topped up fully, and a partial charge does nothing to extend the life of the battery pack. It doesn't hurt it either, but there is no benefit to limiting the charge level to 96%, plain and simple.
    :)
     
  11. TrIPpY

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    I have not measured battery charge outside of the phone. As i already said, i also want my battery fully charged. I don't have that same issue btw (charge dropping a couple of percent after charging till my nexus says 100% and stops charging). Most people will not measure outside of the phone.

    Google states their battery charge indication is accurate btw.

    What i do know for certain is that the bug present in at least Android 2.3.3 and 2.3.4 causes charging to stop prematurely while the screen is off, indicating 95% charge.

    With the workaround i suggested it at least charges till the indicator says 100%. At the very least it's still better than 95%.
     
  12. meat

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    Logisitcs Manager
    Black Creek British Columbia
    Under the settings--battery usage, it displays Emails 54%
    It always showed the display as the top drainer of the battery now it shows emails yet I have only the original 2 email accounts on my phone.

    The other day my phone was rather hot all over. Still havent figured out why.


    Any other users with the same issues?
     
  13. quantumrand

    quantumrand Android Expert
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    Sometimes apps go rogue, getting stuck in a loop that eats up system resources and battery power. This is actually one of the rare times that an automated task killer can be useful, but unless you're using a bunch of poorly written apps, an occurrence like this should be very uncommon.

    If you haven't already, simply rebooting the phone and/or going to "Manage Apps" and killing the Email app will likely fix the issue. If not, explore around in your Email app and see if it's doing anything peculiar (like trying to download a large attachment over and over or something like that).
     
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  14. bfksc

    bfksc Android Expert
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    Just for fun I tried to combine different settings and found a combo that works:

    WIFI tethering and Stay awake

    I charged it last night with these too settings enabled and it worked! The phone charged to 100% and stayed there for about three hours before dropping to 97%. I didn't check if it dropped to 99...98...97, I just checked it after a few hours. The battery display shows that it dropped slowly so it seems to be working. I'll do it again today to confirm it wasn't a fluke and will post the results later.

    :D
     
  15. TrIPpY

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    So a full proof workaround seems a fact that works for both the i9020 (version with super amoled screen) and i9023 (version with ips led screen) to charge until 100%. The "stay awake" option only, works for me (on the i9023 version). But if that only doesn't work, tethering and stay awake enabled together should fix it.

    And now for Google and/or Samsung to fix this weird bug.
     
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