[olpc-nz] Battery LED flashing

[Martin Langhoff]

hi Tabs,

the behavious sounds exactlt like a case of trickle charge. This
triggers when the batt charge is so low that we cannot charge it (or
measure it). When it happens, it's ususlly because a batt has not been
used for a while.

It's normal that it will trckle charge for a while, and then switch to
normal charge and fill it up. If a batt does not get out of  trickle
charge, that prob means it's broken.

In terms of getting more low level info, get your hands  on a script
called batman.fth (it's somewhere in the wiki ;-) ) -- it collects
logs of the batt levels per cell, and you can read it/change it.

hth,



m


On Sun, Jan 3, 2010 at 12:48 AM, Tabitha Roder <tabitha.roder at gmail.com> wrote:
> We plugged in an XO-1.0 with an unknown state LiFePO4 battery (may have been
> fully discharged a week before, or may have been shut down properly) and the
> battery LED flashed instead of coming on solid like charging normally does.
> The battery information in /sys indicated low battery voltage (5.something)
> but otherwise good health and charging state. We tried the battery in a
> different XO-1.0 and the same behaviour resulted. We left it plugged in
> overnight and it appears to have charged normally and the battery now runs
> the laptop (when it was doing the flashing charge, the laptop would switch
> off immediately when you unplug the charger).
>
> http://wiki.laptop.org/go/Power_management#Battery_LED indicates flashing on
> charge means trickle charging. Sadly we didn't find this page when it was
> happening so cannot fully confirm it was flashing orange and with the 4
> blinks, pause pattern. This page also doesn't give any clues as to why a
> battery might be trickle charging.
>
> http://wiki.laptop.org/go/Hardware_specification#Battery suggests that the
> battery has a Maxim DS2756 chip in it, but this chip only monitors one cell,
> so I guess there are two such chips? The /sys interface only gives
> information about the whole battery, it doesn't tell you about the state of
> each cell. The specification pdf on the Hardware_specification page
> describes the Embedded Controller interface to the operating system in terms
> of "Battery", not "Cell" so I guess it doesn't expose each cell either?
>
> Is it possible to see each cell's voltage separately from within the
> operating system or the open firmware? I guess if there is no other way, it
> wouldn't be terribly hard to program a microcontroller to talk to the cell
> monitors over the 1 wire bus.
>
>
> Kind regards
> Tabitha Roder
>
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>



-- 
 martin.langhoff at gmail.com
 martin at laptop.org -- School Server Architect
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