Hey @krenom Krenom,
Thanks for posting so much information about how you accomplished this, we are looking at going down this path one day so you can run the devices off a battery pack and hot-swap between battery packs with the Pi juice inside maintaining power temporarily.
When I was working with the fins, I needed to run with the lowest power consumption possible. To do that I turned off the status LEDs and HDMI port and limited the CPU scaling_governor.
Just in case that helps your use case:
commands = []
if self.our_env['turn_off_hdmi_leds']:
print('Turning off hdmi and leds')
print("We expect two I/O errors here")
commands.extend([
'echo 507 > /sys/class/gpio/export',
'echo "out" > /sys/class/gpio/gpio507/direction',
'echo 1 > /sys/class/gpio/gpio507/value',
'echo 511 > /sys/class/gpio/export',
'echo "out" > /sys/class/gpio/gpio511/direction',
'echo 0 > /sys/class/gpio/gpio511/value'
])
if self.our_env['put_cpu_in_powersave']:
commands.append('echo "powersave"| tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor')
for command in commands:
command_on_host(command)
The status LEDs and HDMI being off doesn’t make much difference, probably less than a tenth of a watt. But the CPU power save mode prevents the CPU from drawing its max load and can bring the max load down from 6 watts to 5. Overall I wouldn’t recommend it because it is probably more efficient to let the CPU draw as much as it needs and then drop back down to its low power state.
As for a bigger case, I felt that need when we had thermal issues with USB power load causing reboots. We designed this lid to replace the stock lid:
Files for the design here
They allow you to use the same screws and can be 3 printed or injection molded depending on your scale. They feel sturdy and but if visuals are important they don’t look good when 3d printed. The design is for 3d printing but we may be revisiting this and if we do I will try and update the forum.
Good luck and thanks for sharing your progress.
-Thomas