Linux – way to control the battery charging port of a laptop

batterylaptoplinux

So here's the idea, i want to be able to control this so as to keep the battery wear level to a minimum.

At >25% , the battery will be in discharge 'mode' and as the battery reaches <25%, I will activate the charging port so that it will charge my battery to 100%, then of course deactivate the charging port.

Note: the charging port will be always plugged in, just disabled when needed.

Best Answer

My first question would be 'why'? If you use your laptop generally on mains, then doing this would mean your battery was generally either charging or discharging. Lithium Ion batteries have a limited cycle life... see http://www.newark.com/pdfs/techarticles/tektronix/LIBMG.pdf which estimates battery life to be of the order of 300 charge cycles. Depending on your laptop and usage on mains you could be running one to several charge cycles per day doing this... killing your battery. I have laptops that are many years old where the batteries still hold good charge (>50% of their original life) because they have mostly been used on mains power and the batteries have not been repeatedly cycled. I have replaced batteries for road warriors who extensively punish their laptop batteries and can kill them to less than minutes life within a couple of years use.

My second question would be 'why'? At some point you will unhook from mains to go mobile and your battery will be down around the 25% capacity mark because it's just about to start charging / just started charging. So there you have a laptop with only 1/4 of it's expected mobile usage time.

My third question would be 'why'? Laptop batteries have dedicated charging circuits that turn off the charge to the cells when they consider they are full and do 'top up' charges as necessary. Judging from the charge LED on my laptops they don't keep charging the battery when it's full. So you're wanting to control externally something the battery is already designed to do.

If you really wanted to do this, you can always 'deactivate the charge port' by unplugging the adapter and plugging it in when the battery is running low. But why would you do this?

Related Solutions

Ubuntu – How to adjust charging thresholds of laptop battery

You need to install tp_smapi-dkms, just do

apt-get install tp_smapi-dkms

When finished, use lsmod | grep tp_smapi to check if module is loaded, to adjust the charge thresholds, do something like this

echo 40 > /sys/devices/platform/smapi/BAT0/start_charge_thresh
echo 60 > /sys/devices/platform/smapi/BAT0/stop_charge_thresh

Add these lines to /etc/rc.local to run them at boot.

This module works at least on X220.

Linux – Lenovo T440s battery status unknown, but charging

This is a common issue with Thinkpad laptops with dual batteries.

When you plug in your laptop it will start by charging BAT0 while BAT1 reports a unknown state. BAT1 will report a charging state when BAT0 is full and BAT1 actually starts charging.

You need to take this into account in your script, and combine values for BAT0 and BAT1 to have something usable :

battery_level=$(("$battery_level_0 + $battery_level_1"))
battery_max=$(("$battery_max_0 + $battery_max_1"))

battery_percent=$(("$battery_level * 100"))
battery_percent=$(("$battery_percent / $battery_max"))

Here is a full example :

#!/bin/sh

path_ac="/sys/class/power_supply/AC"
path_battery_0="/sys/class/power_supply/BAT0"
path_battery_1="/sys/class/power_supply/BAT1"

ac=0
battery_level_0=0
battery_level_1=0
battery_max_0=0
battery_max_1=0

if [ -f "$path_ac/online" ]; then
    ac=$(cat "$path_ac/online")
fi

if [ -f "$path_battery_0/energy_now" ]; then
    battery_level_0=$(cat "$path_battery_0/energy_now")
fi

if [ -f "$path_battery_0/energy_full" ]; then
    battery_max_0=$(cat "$path_battery_0/energy_full")
fi

if [ -f "$path_battery_1/energy_now" ]; then
    battery_level_1=$(cat "$path_battery_1/energy_now")
fi

if [ -f "$path_battery_1/energy_full" ]; then
    battery_max_1=$(cat "$path_battery_1/energy_full")
fi

battery_level=$(("$battery_level_0 + $battery_level_1"))
battery_max=$(("$battery_max_0 + $battery_max_1"))

battery_percent=$(("$battery_level * 100"))
battery_percent=$(("$battery_percent / $battery_max"))

if [ "$ac" -eq 1 ]; then
    plug=""

    echo "$plug $battery_percent %"
else
    if [ "$battery_percent" -gt 95 ]; then
        echo ""
    elif [ "$battery_percent" -gt 85 ]; then
        icon=""
    elif [ "$battery_percent" -gt 60 ]; then
        icon=""
    elif [ "$battery_percent" -gt 35 ]; then
        icon=""
    elif [ "$battery_percent" -gt 10 ]; then
        icon=""
    else
        icon=""
    fi

    echo "$icon $battery_percent %"
fi

Best Answer

Related Solutions

Ubuntu – How to adjust charging thresholds of laptop battery

Linux – Lenovo T440s battery status unknown, but charging

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