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Old 02-15-2010, 05:46 PM   #32
Dan23
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Posts: 73
Karma: 600000
Join Date: Sep 2007
Device: Scribe, Paperwhite 6.8"
A guess at power draw. Calculation are very rough and make many assumptions:
According to this article (a laptop was replaced with a pixelqi screen and tested):
http://www.liliputing.com/2010/01/up...lay-video.html
1. Pixel Qi screen used 2.5 watts of power in normal mode
2. Pixel Qi used .5 watts of power in transreflective mode
A 10 inch Pixel Qi screen was used so this is a valid comparison to Adam

Tegra 2 has been reported as 1/2 watts (http://hothardware.com/Articles/NVID...d-At-CES-2010/)

I do not know how much power other parts consume, but if we assume with wifi off that normal mode is 2.5 (screen) + .5 tegra +.25 everything else while playing hd video, and transreflective is .5 screen+.5 tegra+.25 everything else, we have:
normal Adam: 3.25 watts
transreflective Adam: 1.25 watts

normal - to get 16 hours would require a 16*3.5= 52 watt hour battery
same battery transreflective would provide 56/1.25 = 41.6 hours battery life.

56whr battery is bigger than typical three cells found on notebooks.
If we assume a 3 cell battery with 27 watt hours
normal =27/3.25 = 8.3 hours of battery life
transreflective = 27/1.25 = 21.6 hours battery life

These numbers could be better battery life if other parts consume less and tegra consumes less than .5 while playing hd video (processor is not maxed out)
For example if we used .25 for tegra while playing hd video and .1 for everything else
normal = 27/2.85 = 9.5 hours
transreflective = 27/.85 = 31.8 hours

Even at 0 non screen power usage, if the screen uses 2.5 watts as said, 16 hours is impossible on a 27 watt hour battery. It would require a 40 WHr battery if no other power was used. I have not seen any 3 cell notebook batteries with that many WHrs.

Last edited by Dan23; 02-15-2010 at 05:49 PM.
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