I did try disconnecting internal battery earlier - when it was advised to discharge the batteries. It didn't have any noticeable effect on the thresholds.
Does that mean that you
do know what low and high charge thresholds are set for the internal battery0?
What are they, and what are you using to display them, if not the Lenovo Vantage app?
Can you confirm whether you did or did not set thresholds last year in the aforementioned thread? If you did, the method shown was only for battery0, and may require setting them to 0 (zero) to restore standard behavior, which I believe you may need to do to fix this - if it's not too late.
Installed Windows 11 on some space I had on the second hard drive - don't think i've installed the Lenovo 'Vantage' program yet. I did install the driver update check software and it says things are upto date as far as vendor/Lenovo software goes.
No, Vantage is not a driver, you will need to install it from the Lenovo (NOT the M$) website.
Similarly, Ubuntu updates won't have installed Lenovo BIOS /UEFI updates, only available from the Lenovo site. Go armed with precise model, subtype and existing BIOS version from SETUP boot.
You can use Ventoy to boot the BIOS flash .iso from there.
So i've kind of noticed that sometimes the external battery charging will go upto 100% when I leave it charged overnight and make it sleep (just to save the state of the work i'm doing .... sometimes it will even go off). But right now as I write - it's stuck at 79% despite being plugged in.
In theory it won't use or charge the external battery (#1) until battery0 is charged - but read up on that in the User Guide.
So because battery0 won't charge - either because of wrong threshold settings or it's just stuffed - then battery1 can not charge beyond where it is now. It might however reset its internal chip to 100% after a long time showing 'high' state'.
See below re remaining capacities from your acpiconf -i{0,1} listings.
Doesn't last - switches off.
Might take one of the cheapest batteries available - not inclined to spend on original Lenovo batteries since this is an older/used system
In my experience, a saving of maybe $30 will likely cost you days or weeks dealing with batteries that a) underperform and b) lie to the EC so acpiconf about their state, and c) need replacing again far sooner.
It's also possible that Lenovo may have blacklisted non-genuine T480 batteries?
But it's your time, and money ...
Nope.
I would presume the batter0 is original - but I'm not sure how to check if it is.
OEM info: both LGC (i.e. LG)
bat0: 01AV420 serial 2080
bat1: 01AV490 serial 2838
Genuine Lenovo parts, most likely original.
Ok, other acpiconf highlights, rearranged a bit:
acpiconf -i0
Design capacity: 23940 mWh
Design voltage: 11400 mV
Capacity (low): 200 mWh
Last full capacity: 2440 mWh
Capacity (warn): 122 mWh
[warn: 122 of Lfc 2440 = 5%]
[Lfc: 2440 of design 23940 = 10.2%]
State: critical charging
Remaining capacity: 5%
Present voltage: 11662 mV
~~~~~
So, 5% of 10% = 0.5% of design capacity (apparently) remains.
Notice that warn cap. (5% of last full cap.) is below low cap. (fixed 200mWh, ~0.8% of design cap.) This may indicate a firmware cutoff point?
Cycle Count: 959
Wow, 2.6 years of daily cycling? Sound credible?
~~~~~
acpiconf -i1
Design capacity: 23940 mWh
Design voltage: 11400 mV
Capacity (low): 200 mWh
(same as bat0)
Last full capacity: 4350 mWh
Capacity (warn): 217 mWh
[warn: 217 of Lfc 4350 ~= 5%]
[Lfc: 4350 of design 23940 = 18.2%]
Cycle Count: 455
State: high
Remaining capacity: 79%
Present voltage: 11789 mV
If it were mine I'd be hanging out to use Vantage to view any thresholds set, and
disable them if so - or just replace at least the internal if not.
Good Luck!