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Old 12-22-2010, 06:07 AM   #1
dmalovic
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K3 Real Battery Usage - how many page turns?

Hi!

I tried to read all the battery related kindle posts here, but not very many deal with the K3 battery life. Some users report 30 days of battery, some only a few days, and Amazon even replaced some peoples Kindles on account of high battery usage.

I was checking my ;dumpmessages log file (do a find on 'volt') to see how the battery is behaving. There is also a "def:battinfo:cap" value that shows the capacity in %.

I have 20 already indexed books on the freshly rebooted (hard reset) K3 3G with WiFi OFF and a fully charged Kindle, and in the last days, my battery is down to 60% of capacity, with maybe 4-5 hours of daily reading and many page turns after 5 days?

I am hoping the battery meter is not linear, and that it looses capacity fast at 4.2V, but stabilizes around 3.7 volts to indeed make it possible for the battery to last for a month?! It boils down to a few questions:

1. How does your battery meter go through the life of the battery, linear or dropping fast to about 60% and staying there for a while before finally going down to zero?

2. Is there a way to know how many page turns one does, as that would be the best indication of real battery life, for the K3

3. How long do you wait through the battery low messages before you put the device on recharge?

4. Is there a way to properly form/calibrate the Kindle battery, so the batt meter shows the right capacity? I waited until 3%, which is 65mAh remaining capacity and 3.428V. The full battery is 4.2V and 1873mAh capacity.

Even though I am afraid my K3 might be blowing through the battery too fast, the logs show that it indeed goes through the whole capacity range OK, so I would suspect that people reporting 30 days of battery must not be turning the pages much?
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Old 12-22-2010, 07:18 AM   #2
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I suspect that the majority of people who get up to 30 days on a single charge are probably only using the device for maybe the odd hour of reading most days.

If you're reading for 4-5 hours daily - I would personally class that as quite heavy usage.

I read for around 2-4 hours daily, use a bit of wifi and play the odd bit of music and the battery cycle tends to last around 10-12 days for me. I'm quite happy with that.
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Old 12-22-2010, 07:52 AM   #3
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While I have only recently removed my K3 from the apparently defective unlighted cover, I wonder if it did not contribute to exceptional power usage. Amazon is sending a lighted replacement, but I doubt that I'll expend K-battery cycles powering a reading light when I can continue to use the external light/disposable batteries.

I am working on a recalibration discharge.
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Old 12-22-2010, 09:30 AM   #4
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Quote:
Originally Posted by dmalovic View Post
I am hoping the battery meter is not linear, and that it looses capacity fast at 4.2V, but stabilizes around 3.7 volts to indeed make it possible for the battery to last for a month?!
The discharge curve for a Lithium Polymer battery as found in the Kindle has a very short drop from 100% and then it will plateau off for most of the capacity until when the battery is exhausted at which point it will very rapidly drop in voltage.

It isn't linear at all so estimating the current charge of a Lithium battery isn't simple to do. It relies on known characteristics of that particular type of battery along with historical data on how the battery has behaved along with battery specific calibration data.

Quote:
Originally Posted by dmalovic View Post
2. Is there a way to know how many page turns one does, as that would be the best indication of real battery life, for the K3
Page turns isn't accurate either because of several variables such as time spent between turning pages and what type of book it is. The Kindle is basically a very small thin computer and the workload on the CPU which corresponds to power consumption will vary based on whether its a complicated page and if its ePub/AZW, Topaz, PDF or plain text.

The ambient temperature will also affect the Kindle as the chemistry of batteries is severely affected by temperature.
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Old 12-22-2010, 09:32 AM   #5
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Battery cycles for Kindle WiFi

Here are my battery cycles for the Kindle WiFi after using it for 1 to 2 hours of reading daily and playing one MP3 song daily:

Sep 8, 2010, to Sep 28, 2010 = 20 days
Sep 28, 2010 to Oct 29, 2010 = 31 days
Oct 29, 2010 to Dec 4, 2010 = 36 days
Dec 4, 2010 to Dec 23, 2010 = 19 days

I charge after the message informs me about it on the screen.

Last edited by sirmaru; 12-23-2010 at 08:54 AM.
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