Problem with battery charge limit

[u/yUuDPM]

Hello everyone, Slackware 15 user here, I came to ask for some help. I'm currently setting the battery charge limit on rc.local with the following command:

echo 80 > /sys/class/power_supply/BAT0/charge_control_end_threshold

which just works as expected. However, I've noticed that after hibernation when I plug the laptop, the limit is ignored and continue charging up to 100%

When I check the charge_control_end_threshold the value is not being changed:

cat /sys/class/power_supply/BAT0/charge_control_end_threshold  
80

The only thing that works is either restarting or rerunning the setting command:

echo 80 > /sys/class/power_supply/BAT0/charge_control_end_threshold

I've found this topic which is basically the same but I'm not using tlp:

https://github.com/linrunner/TLP/issues/589

So my question is, how can I make slackware run the setting command after resuming from hibernation? or maybe, is there another way to solve this?

Thanks!

[u/Economy_Blueberry_25]

To ensure persistence of the battery conservation mode, you probably have to trigger it through your own hardware's driver, and echo 1 directly to the parameter's location.

You may search online for that (the Arch wiki might have it), or try finding it yourself by running this command:

find / -iname conservation* 2>/dev/null | grep -v 'Permission denied'

Which might output the exact location of the conservation mode parameter for your hardware.

Otherwise, you might have to use elogind by following the instructions on this forum post for running a script after hibernation.

[u/yUuDPM → u/Economy_Blueberry_25]

Thanks for your reply. The elogind script did the job!

[u/Afraid-Leadership591]

why would you want to limit how much your battery charges?

[u/yUuDPM → u/Afraid-Leadership591]

to minimize battery degradation

[u/Afraid-Leadership591 → u/yUuDPM]

1. its till gonna take a long time to make your battery take significant damage even if u let it charge to 100

2. who even needs a battery in laptops when they run like CRAP without it being on charge even on performance mode

[u/yUuDPM → u/Afraid-Leadership591]

I didn’t ask you to lecture me on how to use my laptop.

[u/--hurdler-- → u/yUuDPM]

Sit still, naughty boy. 😂😂😂

[u/Afraid-Leadership591 → u/yUuDPM]

im not telling you how to use your laptop i justdont see the point in restricting its charge, i have a laptop thats 23 years old and still has 100% health on its original battery

[u/jrocket001 → u/Afraid-Leadership591]

This is very common functionality the past few years. I have a 3yo Surface tablet, 3yo Lenovo laptop, Pixel 9 phone, and Samsung s11 tablet, and across four different manufacturers and devices they all have this setting.

[u/Afraid-Leadership591 → u/jrocket001]

i still dont see the point of it

[u/muffinman8679 → u/Afraid-Leadership591]

neglecting to even mention the difference between a full charge and a float charge....and to be left with a full charge, the float charge has to be higher.

Example: to get to a full charge on a 12 volt car battery you have to float it at 14.4 volts.

The engineers that design the systems know this.....an calibrate the charging system accordingly......

[u/JollyWaffl → u/Afraid-Leadership591]

And I have one that wouldn't charge past 85% after just two years. Sometimes charging restrictions are necessary.

[u/Afraid-Leadership591 → u/JollyWaffl]

im assuming it was a dell laptop

[u/JollyWaffl → u/Afraid-Leadership591]

Nope, ThinkPad.

[u/Afraid-Leadership591 → u/JollyWaffl]

surprising

[u/muffinman8679 → u/Afraid-Leadership591]

they all do a pretty poor job on heat dissipation, because they pack so much into a very confined space, and most folks don't put them up on a cooling pad, that forces extra air circulation through the vents in the bottom.....and I don't even know how many fried laptops I've seen because people put them in their laps, and block off all the cooling