[Gta04-owner] bq27000-battery: battery is not calibrated! ignoring capacity values

[Bob Ham]

On Tue, 5 Feb 2013 09:22:34 +0100, "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:
> Am 04.02.2013 um 16:12 schrieb Bob Ham:

>> For the moment, the software side limits the use of the GTA04 such that
>> it
>> cannot be used effectively when replacing a GTA01 motherboard.
> 
> This is just a limitation on GUI side

It's "just" a limitation in the sense that until it's fixed, anyone with
an upgraded GTA01 "just" can't have a practical phone :-)

> and can be handled by calculating the
> fuel level from battery voltage if the bq27000 is n/a.

There's still the kernel side.  The default kernel contains a bq27000
driver that (1) uses unnecessary resources, and (2) spits out alarming
error messages to the kernel log containing exclamation marks.

The kernel should deal gracefully with a GTA01 battery.  Perhaps the
BQ27000 driver should incorporate a probe function to positively identify a
supported battery.  If a BQ27000 isn't present, the driver should not be
loaded.  There's a question of how to identify a GTA01 battery and what to
do if there's no GTA01 battery and no BQ27000 but that's not an issue for
the BQ27000 driver to worry about.


>> Nikolaus, can you confirm that the GTA04 will operate safely with a
>> GTA01 battery containing no BQ27000? Particularly, will it charge
>> safely?
> 
> It will charge because this is controlled by the TPS65950 using its own
> voltage measurement and measuring/limiting the current flowing into the
> battery.
> 
> So you can not overcharge or damage the battery *by normal operation*.

That's good to know.


> But since you ask for safety: I think, yes there is a small potential
risk
> that we should be aware about.

> The potential risk scenario is that a (partially) damaged battery is
being
> charged and does never reach the end-of charging voltage and gets hotter
> and hotter until ignition and the charging controller has no chance to
> recognize and react accordingly.

> So there is no difference w/o or with bq27000 in the battery. And there
is
> no difference between GTA01, GTA02 and GTA04 being used as charger.
> 
> I.e. all combinations are on the same safety level.

It's good to be aware of this but I definitely feel a little "Eeek!"

-- 
Bob Ham <rah at settrans.net>

for (;;) { ++pancakes; }