Solved! Laptop battery ASUS B31N1726 stuck at 2% and won't charge

[Orongo]

My son's laptop battery went from 97% to 2% and won't charge back.

Here's what I did and tested:
I opened the laptop, removed the battery, examined it, and plugged it back...
AC Wires don't seem damaged, and except for some dust in one fan, battery and other electronic parts look just fine.
Runned the 'battery report' (I just don't know where to attach it...)
Uninstalled the battery driver, and installed it back ('discover hardware')

He basically always keep his laptop plugged (bought less than 3 years ago) but went to visit his grandparents yesterday.
We stopped at a restaurant for about 2 hours, laptop stayed in the car.... (it's winter here)

Windows 11

SYSTEM PRODUCT NAME	ASUSTeK COMPUTER INC. TUF Gaming FX505DT_FX505DT
BIOS	FX505DT.316 01/28/2021
OS BUILD	22000.1.amd64fre.co_release.210604-1628

Battery "name" seems to be FX50442 ...but physically, on it, it's written B31N1726

For the moment... the laptop works only if plugged. Battery remains at 2%.

 

[AlHuneke]

Most vendors provide diagnostic software. I don't know about Asus. Check their web site and download a diagnostic if there is one. Use that to test the battery. I suspect it is shot. Three years is a pretty good life. Keeping a lithium battery at full charge all the time is hard on it, strangely enough. Some vendors (e.g. Lenovo) have an option to only charge the battery to 80%. So does my electric car. That helps preserve the life.