# XO power management

Ismael Schinca ischinca at plan.ceibal.edu.uy
Thu Mar 24 09:25:05 EDT 2011

That's exactly what I wanted to know. How was the SOC evaluated when the
battery lost capacity. If there was some estimation on the battery loss or
just a full capacity assumption and then early poweroff.
I have several batteries, some of them pretty old (that's the idea). A
couple of S/Ns:

00602080616110002384
00602080608110000600

I've been running olpc-pwr-log with depleted batteries to evaluate the
battery condition, but since I wasn't sure how the SOC worked, I didn't know
if the results were valid since I was having different starting points. Some
batteries started from 5%, some from 10%, etc. Now I know that's probably
correct anyways.

Ismael

2011/3/24 Richard A. Smith <richard at laptop.org>

> On 03/24/2011 08:55 AM, Ismael Schinca wrote:
> > Thanks, for starters this is really useful, because it's not at all
> > similar to what I've been observed. The computer powers off with battery
> > levels between 10-15% and the led starts blinking around 5-10%. I'm
> > using several batteries on the same XO 1.0 computer. Granted, the
> > batteries are not fresh ones, but that's exactly what I am trying to
> > figure out. How the battery behaviour changes when battery capacity
> > starts to decrease over time.
> > Any additional information will be most welcome.
>
> What you are observing is exactly what will happen as the battery
> reduces capacity.  We don't have a calibration procedure so the SOC
> assumes 3100mAh.  The SOC is a mAh/1% counter.  After so many mAh it
> subtracts 1%.  The critical level is a voltage reading.  Its not coupled
> to the SOC.  So with a battery that has less capacity you will reach the
> critical level sooner.
>
> Whats the serial number of your battery?  You may also want to run a
> olpc-pwr-log run with that battery so you can determine what the actual
> capacity of the battery is.
>
> --
> Richard A. Smith  <richard at laptop.org>
> One Laptop per Child
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--
Ismael Schinca
Centro Ceibal - Depto. Técnico - I+D
Avda. Italia 6201 - Edificio Los Ceibos
Montevideo - Uruguay.
Tel.: 2601 57 73 Int. 2232
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