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#1 2012-11-12 23:31:32

ego.abyssi
Member
Registered: 2011-07-27
Posts: 45

MacBook Air (4,3) Battery Fried, or Not Recognized?

ACPI reports the following on my battery:

Battery 0: Unknown, 0%
Battery 0: design capacity 7484 mAh, last full capacity 7484 mAh = 100%
Adapter 0: on-line

/sys/class/power_supply/BAT0/uevent shows:

POWER_SUPPLY_NAME=BAT0
POWER_SUPPLY_STATUS=Unknown
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_TECHNOLOGY=Unknown
POWER_SUPPLY_CYCLE_COUNT=0
POWER_SUPPLY_VOLTAGE_MIN_DESIGN=7500000
POWER_SUPPLY_VOLTAGE_NOW=6255000
POWER_SUPPLY_POWER_NOW=0
POWER_SUPPLY_ENERGY_FULL_DESIGN=46800000
POWER_SUPPLY_ENERGY_FULL=46800000
POWER_SUPPLY_ENERGY_NOW=0
POWER_SUPPLY_CAPACITY=0
POWER_SUPPLY_MODEL_NAME=bq20z451
POWER_SUPPLY_MANUFACTURER=SMPNz451
POWER_SUPPLY_SERIAL_NUMBER=

Have I fried my battery, having used up all it's cycles, a logic board issue, or perhaps a driver issue where the battery, power adapter, or logic board are no longer being driven correctly?

Can't seem to get it to charge at all.  At least now, after a few hours off and not charged, then hooked up and booted again, Power Full is no longer 0.  This is irksome.  I don't think that my battery should be so dead all of a sudden.


Fortune sides with him who dares -Virgil

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#2 2012-11-13 03:39:19

nixpunk
Member
Registered: 2009-11-23
Posts: 268

Re: MacBook Air (4,3) Battery Fried, or Not Recognized?

Does the charger light up green or orange?

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#3 2012-11-13 03:49:32

ego.abyssi
Member
Registered: 2011-07-27
Posts: 45

Re: MacBook Air (4,3) Battery Fried, or Not Recognized?

Green...


Fortune sides with him who dares -Virgil

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#4 2012-11-13 03:50:36

WonderWoofy
Member
From: Los Gatos, CA
Registered: 2012-05-19
Posts: 8,412

Re: MacBook Air (4,3) Battery Fried, or Not Recognized?

This happens to me on my Thinkpad, though you are not going to like my fix for it.  What I do is turn the computer off and take the battery out.  Then I plug it in, and push and hold the power button for 20-30sec.  I then unplug while continuing to hold the power button.  Wait another 20-30secs, and then plug back in, still holding, wait a sec or two and let 'er rip by letting go of the button.  It works for me every time, but I know that taking the battery out of a macbook air is no trivial task.

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#5 2012-11-13 04:11:57

ego.abyssi
Member
Registered: 2011-07-27
Posts: 45

Re: MacBook Air (4,3) Battery Fried, or Not Recognized?

No, certainly not trivial, but then I'd have to do it anyway to replace it, which is what I'm trying to avoid.  Not exactly expensive, but not cheap either.  And, if the problem isn't the battery, then I don't want to replace it for nothing.

Does anyone know the reason why this kind of battery problem would happen?  Evidently, it isn't MacBook Air specific...


Fortune sides with him who dares -Virgil

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#6 2012-11-13 04:17:58

WonderWoofy
Member
From: Los Gatos, CA
Registered: 2012-05-19
Posts: 8,412

Re: MacBook Air (4,3) Battery Fried, or Not Recognized?

I am not sure why it happens, but it only happens if I reboot a couple times within a few minutes (like if I am trying a new bootloader or soemthing).  When it does, sh*t goes awry though.  Typically it odes what yours does, tell me that it is 0%, but sometimes it tells me that it is 16243% or some other rediculous number.  And sometimes it just gets stuck at some random percent (for some reason usually from 70-80%) and won't charge anymore.  Fortunately, I usualyl know when I am going to get this, and I now know how to fix it. 

I acutally just tried the fix on a whim while DD-WRTing my router.  They tell you to do a 30-30-30 reset, and it will actually reset the router.  I then read that ti has something to do with the capacitors holding charge for a small period of time after unplugging, so continuing to hold actually gets them to purge the rest of the power they still have.  Otherwise you would be waiting it out.  So I though that just maybe this is what was worth trying on my computer, and it worked.

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#7 2012-11-13 04:39:22

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 13,776

Re: MacBook Air (4,3) Battery Fried, or Not Recognized?

LiIon batteries are wonderful, high energy density batteries that have a nice, flat discharge curve.  They also have a couple characteristics that make them a serious PITA.

When charging, it is critical to monitor their temperature and keep it under control.
When discharging, if the voltage is allowed to drop below a critical voltage, they will (in almost all cases) never charge again.
Over charge cycles, the maximum full charge and the full charge voltage drop.  When that voltage hits the critical discharge voltage, it is game over.

There are some clever charging circuits that monitor the above, and keep a running integration of the number of coulombs into and out of the battery.  If any of the sensors fail to make sense, or if the chip just gets confused, many enter a safe mode to prevent permanent damage to the battery, or worse, cause a nasty hot fire feed by caustic battery innards.


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
You assume people are rational and influenced by evidence.  You must not work with the public much. -- Trilby
----
How to Ask Questions the Smart Way

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