During the last weeks, I spent most of my free time in reading. I also tried to evaluate the battery life of the H2O reader I own and check how it changes according to the light intensity. The statistic function of the device is really helpful for that purpose.
I made four tests. Each time I started with a fully loaded battery, Wi-Fi off, set the light to a fixed value and never changed it. I tried to read ~6 hours per day.
- light at 0%: 77,7 hours of reading (during 12 days, average 6,47h/d)
- light at 15%: 62,0 hours of reading (during 13 days, average 4,76h/d)
- light at 50%: 35,9 hours of reading (during 7 days, average 5,12h/d)
- light at 100%: 17,6 hours of reading (during 3 jours, average 5,86h/d)
According to the manufacturer, customers can expect two months of reading based on 30 minutes/day. It equals to 30 hours of reading (and 59 days of standby which seems to eat a signifiant amount of total battery) which is really nice. But if you read much more than 30 minutes, the total reading time is highly increased! Reading for more than 75 hours without charging the device is really impressive in my opinion. And a real asset of ereader against LCD tablets.
Using the frontlight does not necessary decrease by a significant amount the battery life. With an intensity of 15% the battery decrease by 20%. And with 50% intensity the battery life is inferior by 54%. Therefore a linear relation between light intensity and battery life seems to exist. I guess that using the frontlight at low intensity won't significantly impact the total reading time.
But reading with light at 100% (for whitening the screen in daylight) eats a big amount of power, and the total reading time is decreased by 78% compared to an unlit screen!
Last but not least: making such tests is really, really exhausting
I hope you'll appreciate it
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These values can be compared to what
Julius Caesar did some time ago with it Kindle Paperwhite.
Additional test setting:
— latest firmware used (3.19.5761)
— no Wi-Fi
— KePub format
— ~25 lines per page
— page refresh: 128 pages (patch)
— dictionary use: moderate
— device put in sleep instead of shutting it down