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#1 2023-04-19 20:50:08

oscarcederberg
Member
Registered: 2023-03-20
Posts: 3

[SOLVED ]T480 External Battery no discharge/recharge

hi.

i have a Lenovo ThinkPad T480 with two batteries (BAT0 internal, BAT1 external) and it has worked great so far. however, just a day or two ago the external battery stopped discharging and stays at 100%. this means that the computer shuts off when BAT0 dies, even though the external has charge left. i tried googling around but couldn't find anything for my case except for this unanswered thread from manjaro so i thought it would be fine to post here, hehe.

it is an old battery (4+ years), but i swapped it into another t480 laptop i have with windows, and there it discharges and recharges fine. the amounts also correlate between laptops (discharge the battery from 100%->96% on windows will lead to it being shown as having 96% on arch), so it seems like my arch laptop reads it fine but doesn't use it.

managed to get it to discharge while running

sudo tlp recalibrate BAT1

, but as soon i stop running the program it stays at whatever percentage it is at. i haven't been able to run a full recalibration as it died for some reason after a while.

i've been messing around a bit with polybar and batteries (acpi, reading from sys/class, etc.), so i might've messed something up along the way but unsure what.

output of acpi (i think BAT1 is Battery 2, no idea why there's three of them and unsure if it is even related)

$ acpi
Battery 0: Discharging, 52%, 01:26:41 remaining
Battery 1: Discharging, 0%, rate information unavailable
Battery 2: Not charging, 99%

output of upower for BAT1

upower -i /org/freedesktop/UPower/devices/battery_BAT1
  native-path:          BAT1
  vendor:               LGC
  model:                01AV492
  serial:               2109
  power supply:         yes
  updated:              Wed 19 Apr 2023 10:36:42 PM CEST (23 seconds ago)
  has history:          yes
  has statistics:       yes
  battery
    present:             yes
    rechargeable:        yes
    state:               fully-charged
    warning-level:       none
    energy:              55.82 Wh
    energy-empty:        0 Wh
    energy-full:         55.85 Wh
    energy-full-design:  71.1 Wh
    energy-rate:         0 W
    voltage:             12.75 V
    charge-cycles:       102
    percentage:          99%
    capacity:            78.5513%
    technology:          lithium-ion
    icon-name:          'battery-full-charged-symbolic'

this is the output of upower for BAT0 (for reference):

$ upower -i /org/freedesktop/UPower/devices/battery_BAT0
  native-path:          BAT0
  vendor:               SMP
  model:                01AV421
  serial:               8682
  power supply:         yes
  updated:              Wed 19 Apr 2023 10:36:48 PM CEST (15 seconds ago)
  has history:          yes
  has statistics:       yes
  battery
    present:             yes
    rechargeable:        yes
    state:               discharging
    warning-level:       none
    energy:              10.68 Wh
    energy-empty:        0 Wh
    energy-full:         20.18 Wh
    energy-full-design:  24 Wh
    energy-rate:         6.555 W
    voltage:             11.225 V
    charge-cycles:       272
    time to empty:       1.6 hours
    percentage:          52%
    capacity:            84.0833%
    technology:          lithium-polymer
    icon-name:          'battery-good-symbolic'
  History (charge):
    1681936608  52.000  discharging
  History (rate):
    1681936608  6.555   discharging
    1681936578  5.851   discharging
    1681936548  5.435   discharging
    1681936518  5.785   discharging

thankful for any help!
kind regards

Last edited by oscarcederberg (2023-04-21 14:40:41)

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#2 2023-04-20 13:29:36

linrunner
Member
Registered: 2013-04-21
Posts: 53

Re: [SOLVED ]T480 External Battery no discharge/recharge

Hi,

oscarcederberg wrote:

the computer shuts off when BAT0 dies, even though the external has charge left.

This would normally mean a battery defect.

oscarcederberg wrote:

i swapped it into another t480 laptop i have with windows, and there it discharges and recharges fine.

This in turn proves that the battery is OK and the problem must lie elsewhere.

First thing you should do is to reset the embedded controller (which controls battery functions).  For this purpose, the T480 has an "Emergency Reset Hole" on the bottom side. Shut down the ThinkPad first, then press with a paper clip.

If this doesn't help, then there is a problem with the battery contacts or the system board.

Check the contacts on the battery and on the ThinkPad side. The connector for the external battery sits directly on the board, perhaps a solder joint is defective. To get a better view, you can remove the bottom cover (see Hardware Maintenance Manual p. 65). Please do not forget to deactivate the internal battery in the BIOS first (HMM p. 64).

However, it could also be that something is bent at the battery contacts and the 2nd T480 has better contact by pure chance.

In the worst case, the solution is to replace the system board.

https://download.lenovo.com/pccbbs/mobi … hmm_en.pdf

ps. in no case it is a Linux problem

Last edited by linrunner (2023-04-20 13:32:34)

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#3 2023-04-20 14:47:26

oscarcederberg
Member
Registered: 2023-03-20
Posts: 3

Re: [SOLVED ]T480 External Battery no discharge/recharge

hello!

linrunner wrote:

First thing you should do is to reset the embedded controller (which controls battery functions).  For this purpose, the T480 has an "Emergency Reset Hole" on the bottom side. Shut down the ThinkPad first, then press with a paper clip.

thank you about this tip! had no idea it existed.

the external battery recharges now after BAT0 goes up to 80%. i guess from your description this is controlled by the embedded controller? i'm gonna try to discharge BAT0 now through normal use and see if it switches over to BAT1 when it is low enough or if it shuts off the laptop. i'll get back here as soon that i've found out! thanks in any case smile

it's a bit strange that the internal battery is drained first, form my understanding the external should be the one that is discharged primarily so it can be swapped out with an extra battery (while traveling) without the laptop losing power. is it the embedded controller or the OS that handles the prioritization of which battery should be used?

another note, after pressing the emergency reset hole the TouchPad & TrackPoint stop working. it was strange but the following commands fixed that so no issues, haha:

$ modprobe -r psmouse
$ modprobe psmouse

kind regards

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#4 2023-04-20 15:22:46

linrunner
Member
Registered: 2013-04-21
Posts: 53

Re: [SOLVED ]T480 External Battery no discharge/recharge

The EC alone determines the order in which the batteries are used (discharged) and charged as well as the switching point. Furthermore the Lenovo EC firmware offers no way to change the behaviour (except indirectly via charge thresholds and force-discharge of course). I have also read several times that the behavior varies from model to model.

https://linrunner.de/tlp/faq/battery.ht … ry-powered

ps. only one battery can be charged at a time.

Last edited by linrunner (2023-04-20 15:24:47)

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#5 2023-04-21 14:40:14

oscarcederberg
Member
Registered: 2023-03-20
Posts: 3

Re: [SOLVED ]T480 External Battery no discharge/recharge

thank you, linrunner!!

pressing the button on the back seemed to fix my issue smile great help and informative insight!

i'll set the thread to SOLVED now.

kind regards!

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