Document with answers to most popular battery-related questions is ready

Sebastian Krzyszkowiak seba.dos1 at
Mon Aug 10 14:10:33 CEST 2009

On 8/10/09, Wolfgang Spraul <wolfgang at> wrote:
> Rask,
> I guess it comes down to price.
> Most normal end users won't need the current measurement as they
> don't do development, so adding an extra chip to do the measurement
> either in the device or in every battery might not be worth it.
> Maybe in the device just run a wire to the 3rd battery pin, then sell
> it with a non-Coulomb counter battery normally, and offer the
> Coulomb-counting battery as an add-on for developers?
> Thanks a lot for your excellent feedback, we need to study this more...
> Wolfgang
> On Sun, Aug 09, 2009 at 01:37:00PM +0200, Rask Ingemann Lambertsen wrote:
>> On Mon, Aug 03, 2009 at 01:46:26AM +0800, Wolfgang Spraul wrote:
>> > How are people really using the Coulomb counter in gta02?
>> > Theoretically I would think that it provides far superior power
>> > measurement
>> > options for actual software development, just as you write.
>> > For example when playing with power saving codes, whether in the kernel,
>> > middleware or applications, I would think over the course of several
>> > hours or
>> > days the Coulomb counter data is the primary means for efficient
>> > development.
>>    To me: The clearly most useful part of the bq27000 is the current
>> measurement. You get what seems to be a reasonably accurate measure of the
>> current flow to/from the battery updated every 25 s or so. It's much more
>> practical than an external ammeter: No need to open the case and fiddle
>> with
>> probes, you can measure battery current while in the train, at work or
>> wherever. Having it built in makes accurate current measurement available
>> to
>> many more people in a lot more places.
>>    Here's a few examples where the current measurements have proven
>> useful:
>> 1) Tracking down that current leak from the serial ports into the Calypso.
>> 2) Finding that 8 mA apmd current leak Debian used to have.
>> 3) Confirming the server screen blanker current leak of 38 mA.
>> 4) Measuring the effectiveness of reducing CPU clock and core voltage.
>>    Hopefully it will also help to curb assorted forms of spyware because
>> they will be easier to detect with the power consumption figures readily
>> available.
>>    I don't think it is worth it to spend a coulomb counter on each
>> battery.
>> The selling point would be to keep track of battery degradation, but I've
>> already seen it change its mind from 1067 mAh to 1148 mAh - that's an
>> error
>> of two hours worth of idle time at 100 MHz.
>>    To get a charge level reading, add a voltmeter connected to the battery
>> terminals. As long as the charge and discharge rates are moderate, it will
>> be good enough.

Well, for me user experience when using CC battery is much better when
using dumb battery. I just tested dumb battery on my gta02 yesterday,
and it works fine... but seeing percentage growing up without any
charger connected isn't thing which normal user wants to see ;)

Sebastian Krzyszkowiak

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