MobileRead Forums - View Single Post - iLiad iLiad Power Use: A discussion (or, Leave your stylus at home)

jharker · 10-30-2008, 01:21 PM

As part of my work on battery replacement, I also did some basic power analysis.

Summary:

The Wacom digitizer uses almost no power when turned on and idle (i.e. with the stylus out of the slot).
Ethernet uses plenty of power.
Scribbling uses A LOT of power.
You lose about 7-8 seconds of battery time for every page flip.

My data is based on a program I have that queries the iLiad's battery kernel module. It returns the % charge remaining, estimated time remaining, and most importantly the current draw (in mA) averaged over the past 1-2 seconds or so. I recorded the current every second for 4 minutes under various conditions: with the stylus in, with the stylus out, while scribbling, turning pages, etc.

Here are the details:

Baseline (everything off): 78.0 mA
Stylus out: 80.7 mA
Ethernet turned on: 173.5 mA
Pen out, scribbling continouously in a PDF: 307.6 mA
Page turn forward in PDF: 7.4 seconds lost.
Up arrow pressed in ContentLister: 5.1 seconds lost.

These numbers are rough and may be a bit incorrect.

The last two results are interpreted as follows: Let's say that your iLiad would run 10:00 hours idle. If you turn eight pages, your iLiad will shut down one minute earlier, at 9:59. (8 * 7.4 seconds = ~1 minute.)

Similarly, for every minute you spend continuously scribbling you lose three minutes of battery time. For every minute you have ethernet up, you lose about 1m15s of battery time.

The most surprising thing to me is that the Wacom device appears to use almost no power when on. I thought conventional opinion said that having the pen out shortens battery life substantially? My research says that it doesn't.

So if you want to, you can just leave the original stylus in a drawer and carry around a different stylus. Your battery life won't be affected much, and you can use a more comfortable pen without much inconvenience.

I meant to make this work more extensive and comprehensive, but sadly my thesis demands attention, so I decided to just post what I had. Hope you all find it interesting!

10-30-2008, 01:21 PM	#1
jharker Developer Posts: 345 Karma: 3473 Join Date: Apr 2007 Location: Brooklyn, NY, USA Device: iRex iLiad v1, Blackberry Tour, Kindle DX, iPad.	iLiad Power Use: A discussion (or, Leave your stylus at home) As part of my work on battery replacement, I also did some basic power analysis. Summary: The Wacom digitizer uses almost no power when turned on and idle (i.e. with the stylus out of the slot). Ethernet uses plenty of power. Scribbling uses A LOT of power. You lose about 7-8 seconds of battery time for every page flip. My data is based on a program I have that queries the iLiad's battery kernel module. It returns the % charge remaining, estimated time remaining, and most importantly the current draw (in mA) averaged over the past 1-2 seconds or so. I recorded the current every second for 4 minutes under various conditions: with the stylus in, with the stylus out, while scribbling, turning pages, etc. Here are the details: Baseline (everything off): 78.0 mA Stylus out: 80.7 mA Ethernet turned on: 173.5 mA Pen out, scribbling continouously in a PDF: 307.6 mA Page turn forward in PDF: 7.4 seconds lost. Up arrow pressed in ContentLister: 5.1 seconds lost. These numbers are rough and may be a bit incorrect. The last two results are interpreted as follows: Let's say that your iLiad would run 10:00 hours idle. If you turn eight pages, your iLiad will shut down one minute earlier, at 9:59. (8 * 7.4 seconds = ~1 minute.) Similarly, for every minute you spend continuously scribbling you lose three minutes of battery time. For every minute you have ethernet up, you lose about 1m15s of battery time. The most surprising thing to me is that the Wacom device appears to use almost no power when on. I thought conventional opinion said that having the pen out shortens battery life substantially? My research says that it doesn't. So if you want to, you can just leave the original stylus in a drawer and carry around a different stylus. Your battery life won't be affected much, and you can use a more comfortable pen without much inconvenience. I meant to make this work more extensive and comprehensive, but sadly my thesis demands attention, so I decided to just post what I had. Hope you all find it interesting!