I did some more tests and measurements. It is (and was actually) clear that extra voltage convertors and isolaters in active PoE modules are not without loss. I started with just including them, so not measuring as close as possible to the sink ( 5V 40-pin header) but at the source (12V battery), because that is what counts/matters. But now also did measure boards at microUSB, so just an USB cable and maybe some reverse polarity protection on the board, don't know exact components. So then the USB meter displays:There must be something wrong here, as I see from here:
https://www.pidramble.com/wiki/benchmar ... onsumption
that it should be 1.1 or so.
I now have a nanopineo connected now, same way as Pi2B and idles at 0.84W. That is including a 50 cents DC-DC that does step-down 12V from USB powermeter via passive PoE (3 meters RJ45 cable) to 5V. Is also a 4x Cortex-A7 (AllwinnerH3).
My Pi2B is actually doing random reset/reboot when loaded a bit and supplied with stable/steady 5V, it seems in the past, something is damaged w.r.t. 1-wire GPIO, more I do not know. So that could explain a too high idle power consumption. I guess I first free up a RPi3B from existing enclosure and see how that behaves.
RPi3B RPiOS64 bookworm 6.12.x rpi kernel RF off: 1.26W
RPi2B Raspbian bookworm 6.12.x rpi kernel: 1.57W
NanoPiNEO Debian trixie armhf 6.16.x sunxi kernel: 0.57W
Use-case is idle, or better, basic capability to react to a ping via IP from just a LAN, so networking is up, it is not about off-line computing. I have not looked at optimizations like turn off LEDs. Also no forced low-clock as at least for the RPI3B measured via active PoE it made no difference, clock is already at 600 (is minimum). The NanoPiNEO is 480 minimum (1300 max/load). At least now clear that the own cheap DC-DC module causes about 0.2W loss.
But big question-mark is why is the RPi2B so high? It is a v1.1, so 4x Cortex-A7. Maybe someone can confirm the numbers. The pidramble site states 'nothing plugged into USB', so that means also no ethernet as that is USB connected. I know from long ago that such is killing for power optimizations but up to almost half a Watt seems much too high. That the RPi3B is lower could be in theory because it can do same work in less instructions and bus-width (more the externals) is anyway mostly the same, but also that is old know-how.
Statistics: Posted by redvli — Thu Dec 04, 2025 10:20 am