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Old 11-18-2012, 01:31 PM   #5
hkbeun
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Posts: 6
Karma: 10396
Join Date: Sep 2012
Device: pocketbook 912
Battery life of pocketbook 912, power consumption measuring results

Well as an electrical engineer, I could not resist to measure it with the following results:

Han,
the Netherlands

912 e-reader power consumption measurement with two simple multi meters.

Results:
1) You can read 4 books maximum with one battery charge. Theoretical you could turn about 4500 pages but the continuous consumption of 30 mA will drain the battery more so practical is about 1200 pages maximum with one battery charge.

2) Playing MP3 music or browsing will drain your battery in 4 to 5 hours


Measurement details:

Equipment tested:
Pocketbook 912 e-book with software v2.13 with 8 gbyte SD flash,
battery capacity 1,530 Ah

Turning a page of an epub file on SD memory, current 0,3 amp for about 3,5 sec
Turning a page of an epub file on internal memory, current 0,3 amp for about 4,0 sec
Turning a page of a txt file on SD memory, current 0,3 amp for about 3 sec
So power consumption is typical 0,3 amp while green led is lit

Wifi on, browsing, in rest, no keyboard action, current 0,16 amp
Wifi on, Browsing active, current about 0,3 amp

MP3 player, current about 0,3 amp

No action, wifi off, continuous background power consumption current about 30 mA
E-reader locked, current about 3 mA
Powered down, current about 0,01 mA

Based on above, I estimate you can read without a recharge maximum about 4 books of 300 pages in a few days. About 2/3 of the power will be drained by the 30 mA continuous current, the other 1/3 by turning the pages and some due to the startup/power down.

So reading 1200 pages will drain battery:
1200 pages*0,3amp*(4/3600) equals 0,4 Ah

Based on a reading speed of 40 pages/hour including breaks, you need for 1200 pages about 30 hours, so continuous background power consumption will be:
30 hours* 0,03A equals 0,9 Ah

So total for 4 books 0,4 + 0,9 equals 1,3 Ah. The remaining of the battery capacity of 1,53 Ah will go coffee breaks, power/up/downs.

Browsing or playing MP3 will drain the battery in 4 or 5 hours. 5 hours * 0.3 amp equals 1,5 Ah

Keeping the 912 locked will drain the 912 battery in about 3 weeks 0,003*24*21 equals 1,512Ah

Measuring was done with two simple multi meters. The main meter was in 10,00 amp range, otherwise too much voltage drop across the meter would prohibit the 912 to work/boot. As soon there was a small power consumption, a second lower range current meter was switched in parallel and the main meter decoupled. Measured values could have an error due to the simple setup with DC multi meters and no correction for pulsating current. However results are matching with practical experiences

Last edited by hkbeun; 11-18-2012 at 01:39 PM. Reason: update
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