Cure for battery life: Killing an Android?

Got my eDGe this week and I love it!

But, as expected, battery life and boot time are not impressive. It should be possible to use only the eBook side with everything else completely disabled and so achieve a battery life of several days.
A user wrote in another thread that the eBook side is driven by a separate operating system (Linux). That might be a misunderstanding, because Android itself is based on Linux.
But if it is true: Would it be feasible to implement an option to kill Android (shutdown) and keep only the eBook part alive for reading (devoid of any LCD-related functions, of course)?
Or maybe there could be two choices for booting:
1) Full mode
2) eBook reading only (no LCD screen, no WiFi)
It would be OK if one had to restart the device in order to return to "full mode".

Or, even if the entire device is controlled by Android: Could we not have a dual boot option with a massively stripped down Android that drives the eBook side only?

I don't see why a choose of boot modes would be necessary. It's pretty easy to switch off wifi (literally, there's a physical switch on the LCD side). As for turning off the LCD, adjust the screen off to 30 seconds and then lock the screen. It takes far less time (<10 seconds) to do that then boot (~30 seconds).

Personally, I would find having to reboot it to be able to reactivate either the wifi or LCD to be much more trouble than the small convenience of not having to disable wifi and turnoff and lock the LCD.

Originally Posted by walt526

IIt's pretty easy to switch off wifi (literally, there's a physical switch on the LCD side). As for turning off the LCD, adjust the screen off to 30 seconds and then lock the screen.

Thanks for the feedback. Of course you are right. My theory is that Android is doing something in the background even with the WiFi switch in the OFF position and the LCD screen locked. And these background processes unnecessarily consume energy. I had my device in exactly that state (WiFi OFF, LCD locked). If the eDGe would only be driving an ePaper screen then a fully charged battery should last for days. But it does not. It lasts for less than one day. So therefore I am interested to know whether one could stop Android completely and use only the eBook screen.

Originally Posted by borisb

The eBook side is merely a second monitor. The guts of the system is the LCD side. There is only one CPU, and only one OS - Android (which is a distribution of Linux, yes). Thus, Android has to be running in order for the eBook side to work.

#1 and #2 are already possible. The default is #1 when you boot up the eDGe. To switch to #2, set your screen timeout to a short period (like 2 minutes) and turn off the wireless. An excellent app to make this easier can be found here: http://slideme.org/application/mysettings (I recommend adding the shortcut to the LCD desktop for quick access).

Thanks for the clarification regarding the number of operating systems in the eDGe and the suggestion.

I have a question then: Assuming WiFi switch OFF and LCD locked and an eBook open. I just put my eDGe on the table and do not even turn pages in the eBook. How long does a fully charged battery last in this mode in your experience? In my case it was less than 24 hours. If this is normal for other people's eDGEs then it must be assumed that something else is going on in our devices that uses energy, something in addition to simply "driving" an ePaper screen.

And I would like to know if we could get rid of that overhead while reading eBooks.

If you're looking to get the type of battery longevity that you would from a Kindle or other device that is solely an eReader, then I don't think that is possible. The eDGe uses more capable/powerful (and thus less efficient) hardware than something like a Kindle. It's not a matter simply a matter of a less efficient operating system, the hardware itself is more capable (by design) and thus it uses more power even if the only screen being used is the eInk. It *may* be technically possible to do some tweaking like undervolt the CPU if an eInk-only mode were possible in order to conserve power... but even then, I would imagine that the battery longevity would still be inferior to a dedicated eReader like a Kindle.

Originally Posted by borisb

To significantly stretch your battery life, close the eDGe whenever you're not using it. This puts it into a power-saving sleep mode that can stretch the battery to more than 24 hours by my own informal tests.

If it can be put into sleep mode by closing it, then it can probably be put into the same power-saving mode from software. So, this raises the question: what signals can bring it out of sleep mode? If the only signal that it could possibly respond to is opening the edge, then it's not easy to implement kappert's wish.

But it should be possible in software to implement a mode where it:
- renders a page
- goes into sleep mode
- gets woken up by a page turn button, repeating the process
- have another button that wakes it up fully, returning to normal function

How long does the wakeup process take? 10 seconds? 30? It might not be as responsive if in this mode, and pen input would not be possible, but it would enable very low-power reading.

Originally Posted by borisb

Most people I think see at most 10-11 hours with WiFi off and LCD off. This would be just reading the eBook side. . . .

To significantly stretch your battery life, close the eDGe whenever you're not using it. This puts it into a power-saving sleep mode that can stretch the battery to more than 24 hours by my own informal tests.

Closing the edge when not in immediate use is key. When it goes to sleep it hardly sips any juice out of the battery. I spent the day, about 10 hours, at Wannado (a kid activity center). The edge was put to sleep between activities, and turned back on when my kid was busy. Even using wifi, I had about 40% power at the end of the day. The edge reconnected successfully to the park's free wifi every time it woke up.

Yes, it would be slower, but it could be a useful low power reading only mode. It definitely should not be the normal mode. The LCD and wifi could remain off, with the CPU only coming on to do a page turn.

Thanks for all replies!

Don't get me wrong: I love my eDGe even with the battery life it provides right now. I was only wondering how to squeeze the most out of this platform.

I think there is good hope that we will see some improvements in battery life with Android 2.x versions. Another thing I will investigate is how to easily find and stop processes in Android. As you do not explicitly terminate an application, I suspect they might remain loaded and waste some CPU cycles in the background.

Originally Posted by nprnncbl

Yes, it would be slower, but it could be a useful low power reading only mode. It definitely should not be the normal mode. The LCD and wifi could remain off, with the CPU only coming on to do a page turn.

Yes, exactly, that is what I am looking for! A limited mode that sacrifices most functionality and possibly speed to gain maximum battery life for eBook reading. And yes, it should probably be a hidden feature so the mainstream reviewer crowd won't go on nagging about slow page turn rates (which I find very good in the eDGe, by the way).

In the official enTourage eDGe store (press the shopping cart icon) you can download applications ("Apps").
I found Advanced Task Killer very practical for my purposes. It gives me control over what processes are running on Android. This helps soothe my suspicions regarding unnecessary battery drain, although I have not done any measurements.
Two applications running by default after booting, which I do not need and kill are:

• Alarm Clock

• Email

A word of caution: Other threads warn about killing apps because they might leave data structures in an inconsistent state. So you had better know what you are doing before you go and knock out a running task.

Borisb, kappert were absolutly right in the first post. If you not bootin android, and (if someone port it) boot for example in openink linux, with e-ink support only, it will work for weeks.
Android continuosly run some background jobs. Ok, trully any linux software running background jobs, or at least so called daemons (which monitors some events, like connections or key pressing)... BUT...
The e-ink optimised versions of linux (like openink) have something like zero jobs mode... and (what's more important) Marvell's processor (which used in EE) also have zero power consumption mode. What does it mean? You almost didn't need power for use EE in e-ink mode. The only time, when battery will be used is when new image rendering. So... let's say you need 30 seconds to read an e-ink page. Currently proccessor work in full mode while you reading (30sec) + when reader render next page to display it on e-ink (1sec). In zero power mode processor will work only when you press an button to display next page (1sec). It's 30times improvement in power consumption... Ok... there will be some battery drain to support wacom pen's input. But it's not important (as it use small amount of battery) and you also probably can turn it off.

Originally Posted by kappert

I found Advanced Task Killer very practical for my purposes.

Kappert - any indication yet on if this helped extend battery life? Has it been worth it? Is everything coming to a grinding halt?

it would be cool and useful to have a kind of dual boot selection, open ink vs full laptop/tablet mode. i hope the power to be from edge are listening.

Originally Posted by robot

If you not bootin android, and (if someone port it) boot for example in openink linux, with e-ink support only, it will work for weeks.

Thanks for the data, robot! Yes, that would be a nice thing to have: Dual boot with a dedicated and minimal Linux operating system for the eInk screen and the regular Android.
It is probably quite a lot of work, but it could be worth it... it really might give this device an edge over the competition, so to say :-)