dead battery

William Kenworthy billk at
Wed Oct 1 08:01:52 CEST 2008

These are my understandings from lots of reading and previous posts
between myself and Andy Green and others on the subject - should all be
in the archives.  With 2007.2 I was hit one out of every 3 overnight
suspends ending in a flat battery.  At least with 2008.9 its rarer (but
does happen :(

With the later u-boots, usb default is 100ma as soon as its plugged in.
This unfortunately is less than a running Fr needs.  Normally as soon as
the operating system is up enough, it will negotiate up to 500ma with
the host, or in the case of the wall charger, read the sense resistor
and see that 1A is available.  When the OS is suspended, the PMU manages
the charge until the battery is charged whereupon it switches off - and
stays off.  If the OS is running, it will cycle back on when the battery
level falls to 10-20% (reports vary) as the OS can reset and renegotiate
the charge level.

If the battery is very low (i.e., the internal fail-safe disconnects
it), remove it from the phone for 30 seconds or so.  This allows the
fail-safe to reset (this is what I think happens based on my
observations) so the 100ma can get to the battery, and also reset the
phone hardware - in particular the GSM modem which is directly connected
to the battery and is thought to be root cause by Andy Green - possibly
goes into a wierd state as power drops as well, preventing restart until

The power rail of course drops due to the inrush current much more
during startup with a low battery than normal, causing one chip (USB I
think) to detect a dangerously low voltage and issue a shutdown.  So you
cant get the phone to boot until the battery has had a few minutes of

In my case, USB to my laptop or a desktop machine does it.
Remove/pause/replace battery
plug into USB for 5-10 minutes
remove/pause/replug USB cable and normal boot will happen within a few

The wall charger should work as well, but on my one try it didnt -
possibly because the u-boot wasnt new enough at the time.

Recommendation - use a late (latest!) u-boot.


On Tue, 2008-09-30 at 22:13 -0700, Michael Shiloh wrote:
> > Vince,
> >     When my battery died I plugged my phone into the OpenMoko supplied 
> > charger, started it using NOR boot, leaving it at the boot menu until it 
> > timed out (repeat that twice) then I was about to select boot from the 
> > NOR menu and after a few extra seconds the phone booted.
> > 
> > -Shawn
> >
> I'm confused. I thought that we didn't turn on the charger until we 
> booted into Linux. Am I wrong? Do we charge in u-boot, even at a low rate?
> Michael
> _______________________________________________
> Openmoko community mailing list
> community at
William Kenworthy <billk at>
Home in Perth!

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