Backup battery discharged -> GTA01 and GTA02 dead
werner at openmoko.org
Sat Jul 19 16:09:13 CEST 2008
Rod Whitby wrote:
> Will a backup battery voltage of 0.4V or 0.7V instead of 2.0V cause a
> GTA01 or GTA02 to appear to be completely dead and never power on?
No, it shouldn't have such an effect. But your description does
make me wonder if a sufficiently discharged backup battery might
actually pull down some internal rail in the PMU. That would be
nasty. I'll see if I can create such a scenario.
> Is there a safe way to recharge the backup battery in-circuit when it's
> voltage is this low?
Some people have charged the backup battery by applying power from an
external source. From Seiko's documentation, there are the following
configurations that should work:
2.5V ---[ 3.3kOhm ]---+
3.0V ---[ 10kOhm ]----+
Seiko specify a charging time of 72 hours !
> What is the exact type of battery used for the backup battery,
That should be a Seiko HB414.
> and how is it attached to the board (it seems to be soldered in)
> - what is the easiest way to detach or desolder the current battery
> and install a new one?
Hmm, it's probably messy. Big component, large thermal capacity, large
soldered surface, heat transfer into the PCB, ...
> Will replacing the backup battery on the three "dead" devices bring them
> back to life?
We don't even know why they're dead yet ;-)
More information about the openmoko-kernel