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

Wolfgang Spraul wolfgang at
Mon Aug 10 13:54:03 CEST 2009

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...

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.
> -- 
> Rask Ingemann Lambertsen
> Danish law requires addresses in e-mail to be logged and stored for a year
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