updated watcher posted - thanks
On my machine (dell e7240) running tc-10.x, I get this: $ ls /sys/class/power_supply/BAT0
alarm current_now present uevent
capacity cycle_count serial_number voltage_min_design
capacity_level device status voltage_now
charge_full manufacturer subsystem
charge_full_design model_name technology
charge_now power/ type
..and: $ ls /sys/class/power_supply/AC
device online power/ subsystem type uevent
It looks like watcher is calculating C% from either charge_now or energy_now divided by either charge_full or energy_full.
I get 1742000/2457000=71%, but the watcher display varies slowly between 6.7% and 7.2% - i.e. a factor of 10 out?