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Originally Posted by emellaich
1) You've heard they only use juice when the page turns? Well that is true for the e-ink screen, but not necessarily for the device itself. The processor uses juice as long as it is awake. I believe your Irex has 802.11b? This is sure to burn up a battery if its left on. You might see about turning it off when its not needed. Also, I expect the touchscreen to use some battery capacity.
2) The manufacturer states 8000 page turns. My interpretation of that is more like half that number. When e-ink devices turn the page they first 'blank' the screen with a black flash. My guess is that the flash counts as a page turn, and then the actual page being written is another page turn for the purpose of battery life. You are displaying two pages (a black page briefly, followed by the true page).
3) The idea of page turns also gets funny for me, because I reread books a fair amount. When re-reading I will quickly skip through some pages. However, hitting next page ten or twenty times in a minute takes just as much screen juice as reading those pages and turning them at a slower rate. Therefore, the battery will run out sooner if you are skimming through a book - same number of page turns, but it takes a much shorter time to go through the pages.
4) I do believe that not all batteries are created equal. For example, my daughter had a problem with her cell phone battery and she was told that there were a number of phones of that model that had battery issues, while others were just fine. The bottom line is that any given unit could have a weaker battery in it due to manufacturing variation.
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ad 1) WiFi is a battery killer, hands down. Blue tooth alone cuts battery time in half for most people I know if they have it on all the time, WiFi is supposed to be even worse according to a friend of mine who has WiFi on his mobile. Touchscreens necessarily use energy, how much depends on the technology but as far as I know it's quite a bit. That depends on what you compare it to, though, the Cybook has a rather small battery (you can see that when comparing the time it can play MP3s to any current MP3 player) but it uses so little that it still lasts you several days even if you have it on all the time.
ad 2) Manufacturers always try to give you the highest number they can get in tests. If you insert a brand new, fully charged battery and press page forward as fast as you can (via a program would be best), I am sure you can get very high page counts because the energy used by the processor, card controller and/or RAM makes only a very small portion of the total consumption. When actually reading page presses are rather far in between and therefore the device the energy uses reduces the number of page turns you have left considerably.
In my opinion, though, Bookeen calculated the maximum number rather than try it out: They probably just took the energy consumed by one page turn (most probably the number they got from EInk) and divided the battery max by that number, leaving out the rest of the device entirely.
I activated automatic shutdown after one hour (seems to me a fair compromise, if I cannot get back to my book within that time frame I usually have to finish whatever interrupted me first). With that I can easily get through the week reading on the tube to work and in the evening, whenever I have the time.