battery problems

[James Cameron]

On Wed, Mar 14, 2007 at 04:46:17PM +1030, Joel Stanley wrote:
> $ cat /sys/class/battery/psu_0/capacity_percentage
> cat: /sys/class/battery/psu_0/capacity_percentage: no such device

Odd, on the units I have, I've been using
/sys/devices/platform/olpc-battery.0/psu_0/capacity_percentage

Silly me.
But the path you use gives me numbers, not "no such device".

> the battery does not hold any charge, is the 'no such device' message 
> related?

I've not seen that before.  I don't know if it is related.  Check for it
in trac, and record it if not there.  Include /var/log/messages.

> If so, is there any way to charge the battery?

The newer firmware you have has a trickle charge that may eventually
help, given enough time.  Perhaps that was B2 only though.  Can't
remember.

If you have access to a constant current source, you can apply that to
the battery terminals while monitoring the voltage with a meter.  The
two terminals are the outer pair, the inner one is a data line.
Identify the polarity using a meter first.

I used gold plated 0.1" pitch wire-wrap pins slid down into the crevice
of the battery contact, to measure the voltage.  The pins have a square
cross-section, about 0.6mm thickness.  They can be obtained from Dick
Smith or Jaycar.  I've not tried charging in this way, but I've heard
others have.  Start with 100mA and watch what happens.  The laptop
usually delivers about 1100mA to the battery pack during charging.

If you're not into electronics, I guess I could send you one of my
working batteries, via Australia Post, and have you send me that one for
me to fiddle with.

-- 
James Cameron    mailto:quozl at us.netrek.org     http://quozl.netrek.org/