daveake wrote:The lowest PSU voltage that the my Pi Zero reliably boots from is 2.9V
After reading a lot of warnings on bad USB power supplies over the years, and then this thread , I was confused on the real power needs of the pi . Specifically the pizero. But if daveake and others can run the pi from 3 volts mine should be able to do that too.
So I ran a few tests powering the pizero direct from a lithium-ion cell , including the pimoroni phat dac and a cheap wifi dongle.
And after optimizing the USB cable between cell and pi I must conclude it is a functional setup that does not impact the sound quality to much to be easy detectable in the range 4.2 to 3.0 volts.
Below 2.9 volts ( measured on the GPIO pins 2 and 6 ) Wifi activity is noticeable in the audio output, and streaming stutters.
How ever I could boot the pi with 2.83 volts, and 'run' it up to 2.75 volts , about where it reboots and music was no longer bearable.
This powering method might be of interest to people squeezing the last miliwatts out of their pi setup, when forced to run on batteries and reduce weight.
My first tests were done with a 1 cell ( 18650 ) usb charger to find I could stream music for 5 hours and about 40 minutes before the first reboot.
Next runtime test should be with the exact same cell but without the DC-DC step up regulator. And see how much I do gain from the missing step up regulator and the improved overall efficiency from running on lower voltages.
But of course it must still produce music that does not sound bad.
After that, I will power off the HDMI and the hungry led too to measure that extra saving.
Perhaps under clocking the processor and RAM will help to save even a bit more, so feel free to suggest options for that.
I fed the power though the micro USB for convenience , direct to GPIO should be a bit more efficient..
And even my Bplus with cirrus logic audio card ran well 'way' below 3.2 volts to help drain the cells faster.
Do not take my experiences as the truth, but also do not repeat it if you are not willing to risk to fry your pi.
This is completely outside the designed operating range of the pi, and is pure experimental.
So do not ask me why your pi does not run on your power supply of x milliamp.
Thanks to the foundation for providing is this great little wonder for education of students of all ages.