Good that you updated.
This was necessary, but it is not supposed to fix the issue.
I’m not an expert on batteries but this % seems to me saying that your battery is heading towards the end of its life.
In these cases (maybe I expected with lower %) there are sudden drops from 30-20% down to 0.
Maybe someone more hw experienced can confirm or not if that value is already critical.
There are many hits, all hw-related, searching for laptop sudden battery drop, Eg.
Considering that you have a duration of 2-3hh, I’d think to a battery hw issue rather than end of life.
Good, now go to Garuda Assistant and apply power tweaks and auto cpufreq etc. This may slightly reduce performance but it will improve battery life.
Also, there should be some option to take critical action on given percentage of battery in battery settings. You can modify that.
I also assume now its battery HW issue
but i am just curious why its charging from 20% instead from 0%
So i have a small doubt. it is possible to do that from bios or any OS setting/ Battery saving option to shutdown at certain percentage
This is how batteries work. Over time (or due to failures) they drop immediately at a certain percentage.
I don’t know if there is anything you can do on the BIOS, but I doubt.
In my opinion, a safety trick could be to change in /etc/UPower/UPower.conf
For a depleted battery, it can no longer supply enough juice to fulfill the power draw of the computer. That is why it suddenly shuts down. That is a normal behavior for a Lithium-based battery as it reaches its end-of-life (can no longer hold a charge.)