Subject: Battery info (Re: ACPI userland issues)
To: Steven M. Bellovin <>
From: Daniel Carosone <>
List: current-users
Date: 06/21/2006 08:03:22
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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. =20

(This is very much a UI design issue, of course).=20

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

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.


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