how to minimise RPi2b power-consumption ?

[paul987]

I have not used Rpi, but am considering a Pi 2B for 2 scenarios: general use requiring max power, b) unattended, headless data-logger in IoT environment, where previously SoC like the low-power Seeduino Stalker would be used (in sleep/wakeup mode) to log data - typically true 240V AC energy monitoring.

My questions are:
a) is it possible to run most of the supported OS's for RPi2b, with 3 cores shutdown, and if so, what is the power-consumption (assuming neglible port load)

b) apart from disabling HDMI, is there power-control for shutting down other unused onboard peripherals, eg USB ports

c) for scenario b, is it worth picking a different 240V PSU than the standard PSU used for scenario a

d) for scenario b, what is the power consumption from the wall, using the standard PSU ?

e) for scenario b, is there a standard Li-Ion battery backup solution to cover short-term 240VAC loss ?

[DougieLawson]

a) No. Not that it would make any difference anyway.
b) That can be done. But you may have a hard time using the system if you disable USB as that's the primary I/O channel. The hassle if probably not worth the micropenny savings.
c) 5V0 @ 2000mA is recommended. The RPF "official" power supply does a good job from either a 110V or 230V input.
d) It runs at less than 5W even when the Raspberry is running flat out. That costs about £4.38 per year.
e) No idea. There's lots of LIPO projects but none that seem to have become a recommended option.

[paul987]

a) No. Not that it would make any difference anyway.
b) That can be done. But you may have a hard time using the system if you disable USB as that's the primary I/O channel. The hassle if probably not worth the micropenny savings.
c) 5V0 @ 2000mA is recommended. The RPF "official" power supply does a good job from either a 110V or 230V input.
d) It runs at less than 5W even when the Raspberry is running flat out. That costs about £4.38 per year.
e) No idea. There's lots of LIPO projects but none that seem to have become a recommended option.

Many thanks for your input.

Reason I asked about shutting down cores, is having read energy benchmarks of Android smartphones & their SoC's, the shutting down of uneeded cores saves significant energy, I thought the same would apply to the RPI2b. For purely IoT projects (where data-logging can run off Li-Ion batteries for months) I read the RPi-A is recommended as at 200mA, it takes the least energy of the RPi family - still a lot compared to Seeeduino Stalker's max 22mA. I wanted to experiment using my first RPi in a wider range of scenarios than just IoT, eg a HTPC. That is the reason, I inquired if it is possible to configure the RPi2b to reduce consumption to model A levels.

Your input does not mention any means of reducing consumption implying it is pointless based on annual cost. I had in mind a number of IoT nodes to monitor more than one location, so a power consumption per node of '5Watts' could multiply many times.

Only in last year have I seen mention of RPi recommended for IoT Apps, (previously only Arduino type tech recommended).

When programming and setting up the RPi2, is it practicable to do that from a desktop pc via USB so as to be able to position the RPi remotely, and not have a keyboard and monitor connected to it ? - if so, is there a link to an article on that ?

Can anyone point me to any articles showing means of reducing consumption of the RPi2, eg turning off the HDMI (which I read takes appreciable power), and maybe other power-saving techniques eg underclocking.

Does anybody know of a forum/subforum specialising in using RPi's for low-power IoT configurations ?