Adjust remaining battery power warning threshold

[Matthew Saltzman]

On Mon, 2010-05-24 at 19:04 -0400, Sam Varshavchik wrote: 
> Matthew Saltzman writes:
> 
> > On Sun, 2010-05-23 at 20:48 +0530, Rahul Sundaram wrote: 
> >> On 05/23/2010 08:38 PM, Sam Varshavchik wrote:
> >> > Right now, Gnome shows an alert bubble when I have somewhere between
> >> > 15 and 20 minutes remaining on battery power (varies). When there's a
> >> > couple of minutes left, an automatic shutdown gets initiated.
> >> >
> >> > I would like to adjust the thresholds. I want to be alerted when I
> >> > have about 30 minutes of power left, and initiate a shutdown when the
> >> > battery has 15 minutes of power left.
> >> >
> >> > I cannot find any adjustment knobs in "Power Management" in
> >> > preferences, for this. Are these settings adjustable somewhere?
> >> 
> >> There are gconf keys :  apps -> gnome-power-manager ->  thresholds
> > 
> > Is there one for what level to start recharging at?  My battery manager
> > under Windows suggests that the level should be allowed to drop to about
> > 80% before recharging, to maximize battery life.  But Linux seems to
> > want to recharge at about 97%.
> 
> Huh? Whether or not my battery is charging depends on whether it's getting 
> AC power. If it's on AC power, it charges. When the battery is full it stops 
> charging, and from that point it runs on AC power, without taking the juice 
> from the battery.

Not always.  If you allow the battery to drain just a percent or two and
plug it back in, it won't charge.  If you drain it a bit more, it will.
The Thinkpad battery manager from Lenovo takes that a step further,
suggesting that that recharge threshold should be set lower (and it is
settable)--around 80%.  So even on AC power, the battery won't charge
unless it's been drained below that level.  

The Lenovo folks apparently think that many very short charging cycles
(such as if you usually run plugged in, but suspend to transport the
machine rather than shutting down) or keeping the battery fully charged
for long periods of time without draining it shortens overall battery
life.  Who am I to disagree?

-- 
                Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs