Quote:
Originally Posted by Ravensknight
Umm, I'm glad you did the math and all.
but by about 1/4 of the way down the post, my eyes glazed over and I was wanting to go to sleep.
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Quote:
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Originally Posted by 6charlong:
Your math is impressive but hard for me to follow. My take-away is that when I see an absolute value given for the battery life of a book reader I'm seeing Jabberwocky penned by someone's marketing department, not by their engineers.
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OK. Less words, more intermediate arithmetic.
Definitions:
x. Battery charge per page turn, in per cent, over and above power on usage
a. Battery charge per power on hour, in per cent, over and above sleep usage
b. Battery charge per hour in suspend, or sleep, in per cent
battery_per_day (pages_per_hour*x + a)*hours_reading_per_day + 24*b
days_per_charge = 100/battery_per_day
Data:
1. 25000 pages at 1 second per page.
2. 150 hours at 1 page per minute.
3. 60 days at one half hour reading per day.
Arithmetic:
25000x + 6.9444y = 100%
9000x + 150y = 100%
25000x + 6.9444y = 9000x + 150y
16000x = 143.0556y
y = 111.8446x
9000x + 150*111.8446x = 100%
9000x + 16776.69x = 100%
25776.69x = 100%
x = 0.003879% battery per page turn
y = 111.8446x = 0.4338% battery per hour on time
y = a + b = 0.4338%
60days * 0.5hours/day = 30 hours power on time while reading
30hours * 60minutes/hour * 1page/minute = 1800pages
60days * 24 hours/day = 1440hours in 60days
1800pages * 0.003879% = 6.9822% battery used on page turning in 60 days
100% - 6.9822% = 93.0178% used for idle on time + suspend (sleep) time
a + b = 0.4338%
30a + 30b = 13.014% = 30*0.4338%
30a +1440b = 93.0178%
1410b = 80.0038% = 93.0178% - 13.014%
b = 0.0567%
a = 0.3771% = 0.4338% - 0.0567%
battery_per_day = (60*0.003879 + 0.3771)*0.5 + 24*0.0567 = 1.6657%
days_per_charge = 100.0/1.6657 = 60.03 days for 30 minutes reading per day
From previous post, you can read over 3 hours per day and still get 30 days between charges.
That is the main point. If an Amazon Kindle gives 30days on a charge at 1 hour per day reading, it can not give 60 days at 30 minutes per day. You can not get twice as many days by reading half as long per day on any of these readers unless you completely power off after reading. Even then, the power used by booting up would still keep you from getting twice the number of days. In addition, it would either cut into your reading time or you would need to deal with all the hassel of making sure to turn it on early, but not too early.