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On Android smartphones, when you look into Power settings, it shows a neat usage graph, which usually looks like this (my phone has very similar #s right now):

================ 40%+  Screen

==== 10% OS

==== 8% System

== Y% (Next largest program)

Is there any similar data showing how much battery is eaten by the screen of e-Ink devices, as % of overall power consumption?

Clearly not ~40%, since the whole point of eInk is that it uses a lot less battery. But did anyone quantify it? Plenty of eInk devices run Android so the data ought to be there.


UPDATE: To address clarifications requested:

  • I'm mostly interested in the consumption of power during active reading. But I was greatly amazed to learn that eInk draws no power for displaying unchanging page, so that's a great answer even if unanticipated one :)

  • Rate of page turning shouldn't be a major factor, since I'm only interested in % of consumption (unless device drains battery a lot when displaying a static page?). So any reasonable rate (2-4 pages a minute?) is OK

  • Backlighting should be off or discounted, since I'm interested in eIink consumption, not backlight one.

  • I don't really care about make and model, mostly because for ballpark ranges they should all rate similarly - on smartphones, the screen usage of ~40% seems pretty consistent across devices/models. But we can take some standard eInk Kindle model if necessary to narrow things down; whichever one there's data for.

    But an ideal answer would draw from a study across different eInk devices.

  • Is there a specific device you were thinking about? – aman207 Dec 26 '13 at 7:50
  • @aman207 - If possible it's be more useful if the answer generalizes across a class of devices (e.g. anything with specific eInk type and size 5"). The #s for LCD Smartphones are typically pretty consistent across devices. – DVK Dec 26 '13 at 12:56
  • I think you are curious what eats more power, screen or ebook processing? – Danubian Sailor Dec 26 '13 at 21:00
  • @ŁukaszL. - you can put it that way, roughly. Basically, I want the same graph as the one I displayed for Android phone in my Q. – DVK Dec 26 '13 at 21:42
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I beleive you are asking "can the power usage of an eink screen be quantified?"

As long as you don't change the page/image it is not using anypower.

E Ink's technology is commonly referred to as "bistable". What does this mean? Bistable means that the image on an E Ink screen will be retained even when all power sources are removed. In practice, this means that the display is consuming power only when something is changing. For example, when reading on an eReader, power is only needed when turning to a new page but no power is consumed by the display while reading the page. - See more at: http://www.eink.com/technology.html

To quantify a value for usage while reading you would need to define;

  • The make and model of your device
  • If you are using device lighting and if so at what level
  • The rate of page turning
  • Actually, I'm interested in active usage. But this is a great answer anyway, even if not what I was looking for :) +1 – DVK Dec 26 '13 at 14:39
  • Rate of page turning shouldn't be a major factor, since I'm only interested in % of consumption. Backlighting off, since I'm interested in Eink consumption, not backlight one. Make and model, I'm not sure if they matter for ballpark ranges - on smartphones, the screen usage of ~40% seems pretty consistent across devices/models. But we can take some standard Kindle model if necessary – DVK Dec 26 '13 at 14:39
  • Updated the Question – DVK Dec 26 '13 at 14:48
  • 3
    Rate of page turning is THE major factor. What requires energy (power) is redrawing the screen. If the display is static then an e-ink screen uses no energy (from the device), each page turn will drain your battery. – Fortiter Dec 27 '13 at 0:51
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    @DVK - The thing to realize here is that eInk is not what is being used by the tablet type ereaders (Kindle fire, Nook Color, etc). eInk only requires power to change the image. In theory if you never change the page in 10000 years the e-reader should still have the same page displayed even though the circutry that runs the device has corroded and there is no power... I doubt that the technology will prove that stable in reality but I have an old ereader(like 7 years old) that still has the same page up even though I do not have a battery in the device. – Chad Dec 27 '13 at 14:45
5

The Kindle eInk devices do not run the Android OS, they run Linux. I believe most of the other eInk devices run Linux as well.

That being said, your question is difficult to answer because the energy usage of an eInk screen is so much lower and the way energy is used is very different.

The easiest answer to your question is that 1% is as accurate an estimate for an eInk device as 40% is for the typical Android smartphone. According this page at the MobileRead Wiki, the most common eInk screen takes 750 - 1800 mW during an active update (i.e. turning the page on an ereader) and 1 mW otherwise. Whereas an efficient LED screen will take something like 750 mW constantly (Warning PDF link).

1

There are eink devices out there running Android and allowing access to the system preferences, namely rooted devices. Those can give you exactly that graph. Here is an image of the graph as of my device:

eink device battery usage

But as others noted due to the technology difference the percent value of the display usage does not make any sense here. It is not very helpful without context for "normal" Android devices but here you can't draw any meaningful consequences from it. "Mobilfunk-Standby" (cellular standby) doesn't make much sense also.

Plus this was just taken after unplugging. Maybe I can take another photo in a few days with more useful data, according to my usage (which differs from using it only for reading, that was the whole point of rooting).

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