[mergen3107]

Here is what is available for Kobo Clara HD in battcalc.sh:

# Battery Statistics Calculator 1.1 (2024-05-25) by Aleron Ives
# Modified for Kobo Clara HD by mergen3107
# This script calculates battery statistics for the Kobo Libra 2.
# Check the contents of /sys/class/power_supply/ if you use a different
# model to ensure that the statistics you want to track are available.
#
# You can use NickelMenu to invoke this script like so:
# menu_item :main :Battery :cmd_output :500 :/mnt/onboard/.adds/battcalc.sh

# Gather the necessary statistics
meter=$(cat /sys/class/power_supply/mc13892_bat/capacity)
v_now=$(cat /sys/class/power_supply/mc13892_bat/voltage_now)
health=$(cat /sys/class/power_supply/mc13892_bat/health)
temp=$(cat /sys/class/power_supply/mc13892_bat/temp)

# Format the statistics
let v_now/=1000;
let temp/=10;

echo Capacity: $meter %
echo Voltage: $v_now mV
echo Health: $health
echo Temperature: $temp °C

"Health" is only a word ("Good" in my case).

Thanks everyone for NickelMenu and this script!