Calculating how much time we have left…

GNOME Power Manager sometimes really gets the time remaining wrong. It doesn't help that the ACPI BIOS sometimes misrepresents the data values, the units, or just gives bogus readings, but we should at least try to be accurate.

So I've been playing with a historical correction-matrix approach, at the moment targeted to the li-ion discharge curve. Initial results are very encouraging, and appear to be much more accurate than relying on the embedded controller data for my dual core laptop and my old iBook. Factoring in battery temperature would likely give an even more accurate answer.

And then I stumbled on this patent.

It appears to patent a method of reading the battery total energy and dividing it by the discharge rate, and then correcting it with a chemistry profile and specific historical correction matrix. Ahh…

This seems fairly obvious calculation to me, and I would hardly call it an invention (it's a formula with method), but I do not want to put a feature into g-p-m that is clearly patented. The patent would also likely explain the lack of documentation available online, and why all of the battery discharge chips are very closed source.

So, where do I go from here? I've not released any code, but I would appreciate your advice about what to do.

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Richard has over 10 years of experience developing open source software. He is the maintainer of GNOME Software, PackageKit, GNOME Packagekit, GNOME Power Manager, GNOME Color Manager, colord, and UPower and also contributes to many other projects and opensource standards. Richard has three main areas of interest on the free desktop, color management, package management, and power management. Richard graduated a few years ago from the University of Surrey with a Masters in Electronics Engineering. He now works for Red Hat in the desktop group, and also manages a company selling open source calibration equipment. Richard's outside interests include taking photos and eating good food.

One thought on “Calculating how much time we have left…”

  1. Now that you've stumbled on a patent and said so publicly, you may have painted yourself into a corner (triple damages, etc). Often there's a way to work around a patent, by doing the design in such a way that it doesn't exactly match the claims. Eben Moglen's Software Freedom Law Center might be able to help. Joe Buck (GCC steering committee)

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