
Raspberry Pi Zero Power Consumption Comparison - geerlingguy
http://www.midwesternmac.com/blogs/jeff-geerling/raspberry-pi-zero-power
======
geerlingguy
Just posting the tl;dr at the top of the article:

 _The Raspberry Pi Zero uses about 1 /3 the power of the A+, or 1/6 the power
of the model 2 B._

This is pretty awesome, as it's only about twice the power usage of a typical
Arduino setup, so battery-powered embedded projects can start considering the
Pi as an option. It helps, of course, that this is just $5!

I just got my mini-HDMI adapter in the mail today, so I'll be running a few
more tests to see if there are any other major differences between the Zero,
the model 2 B, and the A+/B+ (I currently use the A+ for most small projects
right now, and the 2 B when I need a little more CPU).

~~~
swiley
The power consumption was the number 1 reason I couldn't use the PI in most of
my projects so this is super exciting (the number 2 being cost).

~~~
throwawydfje
if power and cost were 1 and 2 this is pretty good for you! Could I ask what
the specific applications were? I'm very interested and wonder what other
people have done. May have follow-up questions for you :)

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mike-cardwell
I'd really like to find a USB battery pack for one of these which can be used
to make the device portable. I know there are loads, but they usually have one
or more of the following problems:

1.) Can't power the PI at the same time as being charged

2.) PI consumes power faster than the battery can charge up

3.) Neither of the above two problems, but when you plug the battery into the
mains it momentarily disrupts the PI causing it to reboot.

Anyone know of a battery which will last with one of these for the best part
of a day or more and which I can just plug into the mains when I'm near a
socket to keep it topped up?

[edit] FWIW, my plan (if I can sort the power) is to migrate my email and xmpp
services from the fixed in place Intel NUC under my TV at home, to a Pi Zero
in my backpack.

~~~
bapbap
I am not a battery or electronics expert but my understanding is that it is
not ideal to simultaneously charge and discharge a LiPO battery, so most don't
support passthrough.

I use a RAVPower Xtreme (26800mAh - though I'm not sure if I believe that
rating) to power a dashcam and had similar requirements to you. However, I've
implemented a DPDT relay and a 12V boost regulator to switch between the
battery pack and car power (ACC), depending on the ignition status of the car.
So when the car is on, the battery is being charged only and the dashcam is
getting power from the car. When the car is off, the battery is only being
used to power the dashcam.

I've not tested it with a Pi but there is not an interruption in power long
enough to disturb the dashcam (the relay spec is 8ms operate time). The
battery pack is charged using a 2A 5V charger. I can't properly assess the
charge status/history of the battery as it only has 4 LED's and I don't want
to take it apart but so far my commute and other driving is long enough to
keep it ticking over.

~~~
disposeofme123
Its definitely possible, think about the circuitry in your phone and how the
batteries work with that.

As far as I'm aware, most modern phones can't turn on without a battery pack
present in the phone, even when plugged in, which would suggest that the juice
is actually coming from the phone battery at all times and not direct from the
charger regardless of charging state.

------
throwawydfje
Very interesting. Still far from solar-powered territory for outdoor projects,
for example. Unless there were a way to wake the pi very easily. However, the
raspberry pi includes no power management whatsoever; it's either off or
on[1]. Why not? Does the chip not support it?

\--> Note that the article specifically calls out disabling USB, disabling
ethernet (not relevant here), and disabling video output if not using it. I
wonder if the author could try disabling HDMI to see if power is reduced....

This can be mitigated if there were a way to boot quickly on demand. See this
writeup on sleepypi, an expansion-board that does just that:[2] So it should
be possible to wake on demand by powering up and going through a boot cycle.
Since the hardware is SO very fixed (not going to change short of ripping
parts of the board off) I wonder why the boot time couldn't be further
reduced...what really takes 10 seconds, during which the SD card could have
read 200 MB or so? It's nearly enough time to wake from hibernation, were that
supported. (SD card bus speed is limited to reading 20 MB/second or so). I'm
sure it could be improved.

This other write-up mentions using the previous generation for up to 24 hours
for remote-location time-lapse photos [3] - also contains an interesting idea
about underclocking. Not sure if this suggestion is relevant, possible, or
works.

[1] No sleep mode on pi:
[http://raspberrypi.stackexchange.com/questions/4773/raspberr...](http://raspberrypi.stackexchange.com/questions/4773/raspberry-
pi-sleep-mode-how-to-avoid)

[2] * Pi and SleepyPi: [http://marktmarshall.com/2014/08/experimenting-with-
raspberr...](http://marktmarshall.com/2014/08/experimenting-with-raspberry-pi-
power-management/)

* An interesting FAQ on SleepyPi: [http://spellfoundry.com/sleepy-pi/sleepy-pi-faq/](http://spellfoundry.com/sleepy-pi/sleepy-pi-faq/)

[3] Powr saving on raspberry pi A in remote installations:
[http://babaawesam.com/2014/01/24/power-saving-tips-for-
raspb...](http://babaawesam.com/2014/01/24/power-saving-tips-for-raspberry-
pi/)

~~~
bootload
_" I wonder if the author could try disabling HDMI to see if power is
reduced...."_

from comments ~
[http://www.midwesternmac.com/comment/3216#comment-3216](http://www.midwesternmac.com/comment/3216#comment-3216)
in this article, _" Controlling both the PWR and ACT LEDs on the Raspberry Pi
2"_ ~ [http://www.midwesternmac.com/blogs/jeff-
geerling/raspberry-p...](http://www.midwesternmac.com/blogs/jeff-
geerling/raspberry-pi-zero-power)

~~~
throwawydfje
(could you clarify why you include the second link? Your second link is our
article link.)

The comment that you mention mentions savings of "28ma" \- could it really be
so high? This is hard to believe, or hard to believe that it would translate
the raspberry pi zero, as our article link says the idle is 50-70 mA (third
photo caption on page) - so if true and the same for this board, disabling
HDMI would reduce current by up to 56%! However, on the other hand that might
not be true at all. Perhaps the A has a dedicated chip for HDMI, whereas this
chip drives it directly; or perhaps the hearsay on current savings from the
HDMI is simply wrong. I've submitted a version of this comment as a comment to
the author's blog, since he's all set up to investigate. (I think the post is
pending moderation.) Probably there will be 0 power savings.

EDIT: Thanks, author!

~~~
geerlingguy
I just tested this three times, and it looks like it's right around 30 mA
saved, so the rumors are true!

I'm going to tinker a little bit and see how low I can get the power
consumption (disable HDMI, disable LED, and just have Pi running by itself).
I'll post back here with more details.

~~~
throwawydfje
Wow! That is an astounding difference. Thanks for your quick action. If your
numbers are correct looks like you just reduced idle usage by close to 50% -
0.2 watts to 0.1 watts or something - if a solar panel has to get through fog
and night-time on an attached battery, that is a _huge_ difference!

~~~
geerlingguy
Running barebones I can get down to 40 mA at idle. Almost Arduino territory!

~~~
throwawydfje
going to sleep so you won't be getting more comments from me, but thanks for
the interaction and your article! great result. I hope you'll have a chance to
incorporate the new numbers/savings into your write-up.

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geerlingguy
Just did a bunch more testing, and I can get it to idle at ~40 mA if I disable
HDMI (inside `/etc/rc.local`: `/usr/bin/tvservice -o`).

With a WiFi dongle (so it can operate on the local network at least) and HDMI
disabled, it hovers around 120 mA. Very, very nice!

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pen2l
> _The Raspberry Pi Zero - quite a small Linux computer!_

Okay, I have a smalllll complaint. In popular modern-day English, R-pi is not
really a 'computer'. Because you can't run a full-fledged operating system
like Windows or Linux on it -- you have to run embedded version of those OSs
(like Windows CE or whatever). I think I may not be totally and technically
correct in my point here, but I think it's an important point to make or at
least mention somewhere along the way anyway -- because, as it happens, I told
someone that R-pi is basically a cheap computer... and this person was
eventually miffed to find that he couldn't run the Windows applications he
wanted to run on it, because those applications only could run on a x86
Windows install.

~~~
pjc50
The solution to "cheap windows" is the various Bay Trail devices; so far the
best offer I've seen is 7" tablet for £45 which comes with a year's
subscription to Office 365 (worth >£50).

~~~
hobbsy
do you have a link please?

~~~
pjc50
[http://www.amazon.co.uk/gp/product/B00O636WJU](http://www.amazon.co.uk/gp/product/B00O636WJU)
(price has gone up a bit)

