Raspi UPS HAT was a board for Raspberry Pi with a controller and a LiPo battery that act like an UPS. On board, there's a MAX17034 chip (connected to i2c bus) that could be asked for battery voltage and remaining capacity (0-100%). With this simple script, far to be perfect (and you are encouraged to fix and improve it !), you can shutdown safely your RPi when battery on UPS Hat reach a critical level, avoid any potentials data loss.
You need to install smbus2 with sudo pip install smbus2
Installation is pretty simple: just do python setup.py build and sudo python setup.py install. If you want to execute as a daemon on startup, just copy raspiupsmonitor.initd to /etc/init.d (cp raspiupsmonitor.initd /etc/init.d/raspiupsmonitor, sudo chmod +x /etc/init.d/raspiupsmonitor, sudo update-rc.d /etc/init.d/raspiupsmonitor defaults) and the wrapper raspiupsmonitor.sh to /usr/local/bin.
Then you can use it as other system services with:
/etc/init.d/raspiupsmonitor [start|stop]
Configuration is in raspiupsmonitor.cfg must be copied to either
/etc/raspiupsmonitor.cfg ~/.raspiupsmonitor.cfgraspiupsmonitor.cfgand the relevant part is [Monitor]:
[Monitor]
# On alert level of 10%, just alert all users...
alert_level=10
alert_action=/usr/bin/wall "UPS Battery is dying..."
# When battery is dying, halt the system safely
critical_level=5
critical_action=/sbin/halt -p"level" is the percentage of power remained, in a range from 0 to 100. When battery is discharging and reach the alert or critical level, "action" was executed.