Raspberry Pi Zero Power requirements
Peggy is build on the low power pi zero. So I want to discussed the Raspberry Pi Zero Power requirements. When we talk low power I mean very low power. Pi zero on boot takes in around 120 mA of power. When the Pi is idle and Ethernet, HDMI, LED’s disabled consumption is a mere 80 mA
I currently do not have an Ethernet installed to check the power consumption with it.
Raspberry Pi zero without Ethernet
|Pi State||Power Consumption|
|Powering on||120 mA (0.7w)|
|Idle||80 mA (0.4W)|
||250 mA (1.2W)|
||200 mA (1.0W)|
How to reduce the power
|Disable HDMI||25mA||Add the following to /etc/rc.local to disable HDMI on boot
to re-enable just change the command to
|Disable LEDs||5mA per LED||I personal want LEDs to give a visual status but if you don’t care just rip them off the board or, add the following lines to your Pi’s
Peggy’s hardware side of the project will start with power from 18650 batteries. The hardware goal is to have Peggy only run off these batteries and not take any power from the grid IE solar charged batteries.
Lets do some math
The cluster has 20 nodes * full load 1.0 W = 20 W of of power or 20 nodes * 200 mA = 4 A
Selecting the best condition 18650 batteries I have in stock are they average 1.5 A or 3.7 v * 1.5 = 5.5 W therefore a node should be able to run at full power for 5 hours ( 5.5W / 1 W ) in ideal condition with one battery.
If any of you are wondering I am not using the Amp rating it is due to the 18650 having a stable voltage of 3.7 V this needs to go threw a boost converter to become 5 V. This conversion is about 95-97% efficient so we lose some of the battery capacity. In addition we can not run the batteries down to 0% but 20-30%.I am currently ignoring this as my amp rating of the batteries include only usable amperage.
Back to the setup, I would like a node to run for 24 Hrs without needing to be charged therefore 5 batteries per node are needed. 5.5 W * 5 = 27.5 W (24 W requirement)
Using the above math 27.5 W * 20 nodes = 550 W. Or 100 batteries * 1.5 A = 150 A
Charging the battery’s would cost a total of a .550 KW * $0.32 per KW (I know very high) = $0.176 per day