A guide to power off the Pinephone on low battery

I created a lowpoweroff script for the Pinephone and Pinephone Pro to help prevent over-discharge by forcing a power-off below a certain capacity.

It loops through all power sources the kernel is aware of and enforces a minimum capacity rule that powers off the system if a battery is below a certain threshold (default: 5%) and not charging.

Install the lowpoweroff script

# Create /usr/local/sbin if it doesn't exist
# and set privileges if it's been newly created
sudo mkdir /usr/local/sbin && sudo chmod 755 /usr/local/sbin

# Install lowpoweroff
sudo touch /usr/local/sbin/lowpoweroff
sudo chmod 755 /usr/local/sbin/lowpoweroff
sudo vi /usr/local/sbin/lowpoweroff

# Paste the following:
#!/usr/bin/env bash
# License: BSD 0-Clause, Ulfnic
Err(){
	printf '%s\n' "$2" 1>&2
	[ $1 -gt 0 ] && exit $1
}

while [ "$1" ]; do
	case $1 in
		--test|-t)
			Test=1 ;;
		--min-capacity|-m)
			MinCapacity=$2
			shift ;;
		*)
			Err 1 "Unrecognized option: $1" ;;
	esac
	shift
done

# Apply default to minimum battery capacity and validate
: ${MinCapacity:=5}
Re='^[0-9][0-9]?0?$'
[[ $MinCapacity =~ $Re ]] || Err 1 "Unrecognized minimum battery capacity: $MinCapacity"

BatteryPathCount=0
for BatteryPath in /sys/class/power_supply/*; do
	[[ $Test == 1 ]] && printf '%s\n%s\n' "=== $((BatteryPathCount++)) ===" "Battery: $BatteryPath"

	if [[ ! -f "$BatteryPath/type" ]]; then
		[[ $Test == 1 ]] && printf '%s\n' "Skipping, battery type file not found at: $BatteryPath/type"
		continue
	fi
	BatteryType=$(cat "$BatteryPath/type")
	[[ $? > 0 ]] && continue
	[[ $Test == 1 ]] && printf '%s\n' "Type: $BatteryType"

	if [[ $BatteryType == 'Battery' ]]; then

		# Fetch and act on battery status
		if [[ ! -f "$BatteryPath/status" ]]; then
			[[ $Test == 1 ]] && printf '%s\n' "Skipping, battery status file not found at: $BatteryPath/status"
			continue
		fi
		BatteryStatus=$(cat "$BatteryPath/status")
		[[ $? > 0 ]] && continue
		[[ $Test == 1 ]] && printf '%s\n' "Status: $BatteryStatus"

		if [[ $BatteryStatus == 'Discharging' ]] || [[ $Test == 1 ]]; then

			# Obtain battery capacity and poweroff if it's below minimum threshold
			if [[ ! -f "$BatteryPath/capacity" ]]; then
				[[ $Test == 1 ]] && printf '%s\n' "Skipping, battery status file not found at: $BatteryPath/capacity"
				continue
			fi
			BatteryCapacity=$(cat "$BatteryPath/capacity")
			[[ $? > 0 ]] && continue
			[[ $Test == 1 ]] && printf '%s\n%s\n' "Capacity: $BatteryCapacity" "Minimum Capacity: $MinCapacity"

			# Validate battery capacity format
			Re='^[0-9][0-9]?0?$'
			if [[ ! $BatteryCapacity =~ $Re ]]; then
				[[ $Test == 1 ]] && printf '%s\n' "Skipping, battery capacity format is incompatible: $BatteryCapacity"
				continue
			fi

			if [[ $BatteryCapacity < $MinCapacity ]]; then
				if [[ $Test == 1 ]]; then printf '%s\n' "Battery below minimum capacity, this would trigger poweroff"
				elif [ -f '/usr/sbin/poweroff' ]; then /usr/sbin/poweroff
				elif [ -f '/sbin/poweroff' ]; then /sbin/poweroff
				else Err 1 'poweroff not found'
				fi
			fi
		fi
	fi
done

Test lowpoweroff script

Normally lowpoweroff is quiet unless there’s an error. Adding --test performs a dry-run and displays a readout of every power supply value it’s reading. If the script is working and USB is plugged out, this test should say “Battery below minimum capacity, this would trigger poweroff”.

# Plug in USB power
sudo /usr/local/sbin/lowpoweroff --test --min-capacity 100
# Unplug USB power
sudo /usr/local/sbin/lowpoweroff --test --min-capacity 100

Make it a daemon

lowpoweroff needs something to run it once every minute. Choose from Option 1 or 2 below this post for the method most suitable to your operating system.

If you’d like to set it up differently, here’s some example commands you might want to use:

# Auto-poweroff at the default 5% capacity
/usr/local/sbin/lowpoweroff

# Auto-poweroff at 3% capacity
/usr/local/sbin/lowpoweroff --min-capacity 3
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Option 1. Setting up lowpoweroff with systemd

Create the timer that’ll run lowpoweroff 3 minutes after boot and every minute thereafter:

sudo vi /etc/systemd/system/lowpoweroff.timer
# Paste the following:
[Unit]
Description=Power off if battery capacity is too low

[Timer]
OnBootSec=3min
OnUnitActiveSec=1min

[Install]
WantedBy=timers.target

Create the service to be run by the timer:

sudo vi /etc/systemd/system/lowpoweroff.service
# Paste the following:
[Unit]
Description=Power off if battery capacity is too low

[Service]
Type=oneshot
User=root
Group=root
ExecStart=/usr/local/sbin/lowpoweroff

Initialize the service:

# Recognize the new unit files you made
sudo systemctl daemon-reload

# Start the service and check it's status
sudo systemctl start lowpoweroff.timer
sudo systemctl status lowpoweroff.timer

# If it's running correctly, enable it so it starts on boot.
sudo systemctl enable lowpoweroff.timer
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Option 2. Setting up lowpoweroff with cron

Verify crond is running. If not follow the appropriate steps for your init system and make sure it’s enable to run at boot.

# === FOR: Systemd === 
sudo systemctl status crond
# If not runing:
sudo systemctl start crond # Start service
sudo systemctl status crond # Confirm working correctly
sudo systemctl enable crond # Start crond at boot

# === FOR: OpenRC (PostmarketOS) ===
sudo rc-service crond status
# If not runing:
sudo rc-service crond start # Start crond
sudo rc-service crond status # Confirm working correctly
sudo rc-update add crond # Start crond at boot

#  === FOR: runit ===
sudo sv status crond

Add the script to the root crontab set to run every minute:

sudo crontab -e
# Paste the following in a new line and save
*	*	*	*	*	/usr/local/sbin/lowpoweroff
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