[Novalug] Laptops

Mike Shade mshade@mshade.org
Mon Oct 13 15:34:03 EDT 2008


Dan,

Another aspect is that the estimation can grow less and less accurate over
time if the battery hasn't been drained to 0 in a while.  Let the battery
run down almost completely and recharge fully.  You may find the meter
becomes more accurate after that.  Note, this has nothing to do with the
"memory effect" I know a bunch of you are about to jump on me about :)

-- Mike

On Mon, Oct 13, 2008 at 2:46 PM, Gregory Maxwell <gmaxwell@gmail.com> wrote:

> On Mon, Oct 13, 2008 at 9:53 AM, Dan Arico <dan_arico@aricosystems.com>
> wrote:
> > Can anyone give me some insight on how battery life is calculated on
> laptops?
> >
> > I have a Lenovo 3000 running Ubuntu 8.04. When I fire it up, the little
> batery
> > symbol tells me I have 1 hr 45 min of battery time left. After using it
> for
> > 45 minutes (web browsing), it tells me I have 1 hr 30 min left.
>
> It depends. ACPI reports the current power usage, and the batter
> itself reports the current capacity remaining.  Simple arithmetic gets
> you an answer, though it's often a wrong one.
>
> The problem is two-fold:  Your usage isn't constant, and the
> batteries' prediction is pretty inaccurate.
>
> Some of the GNU/Linux battery monitoring stuff (i.e. the gnome battery
> monitor shipped in fedora 9; perhaps Ubuntu ships the same software)
> tries to be a bit smarter: It monitors how the values change over time
> and discovers an adjustment to true up the lifetime estimates.  In
> theory this should work fairly well but I have never bothered checking
> myself.
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