Subject: Re: Battery info (Re: ACPI userland issues)
To: Daniel Carosone <>
From: Steven M. Bellovin <>
List: current-users
Date: 06/20/2006 19:50:20
On Wed, 21 Jun 2006 08:03:22 +1000, Daniel Carosone <>

> On Tue, Jun 20, 2006 at 01:57:12PM -0400, Steven M. Bellovin wrote:
> > 	This does pose an interesting question about what battery
> > 	status tools should display.  sysutils/asapm, which has
> > 	been patched to use the envstat interface if available,
> > 	gives battery percentage relative to the design capacity.
> > 	apm (and Windows) seem to give it relative to the last full
> > 	charge.  It isn't clear to me which is correct.  
> (This is very much a UI design issue, of course). 
> Of the two you describe, I think the Windows behaviour is likely more
> useful.  It does hide the battery degradation over time, but users
> would be likely be confused if they saw the battery was failing to
> fully charge no matter how long they left it, without some other
> indication.
> What might be best is a battery bar display that shows the design
> capacity on the full scale, and marks the difference between that and
> the last full as "inaccessible" (eg, in some other colour), and then
> the normal bar in the remaining space.  Perhaps clicking on it or
> hitting some other 'zoom'-like widget could toggle between showing
> this, and narrowing to just the last full range.
> All that said, though, I have my doubts about the accuracy (or, at
> least the practical interpretation) of these figures for real run
> time, even at constant draw, especially once batteries are older.
Agreed, on all points.

		--Steven M. Bellovin,