Power Management
Matthew Garrett
mjg at redhat.com
Tue Feb 17 02:32:39 UTC 2009
On Mon, Feb 16, 2009 at 07:02:52PM -0500, brad longo wrote:
> As I'm sure most of you know, leaving your laptop plugged in and
> charging with a full battery charge is harmful for the battery. I have
> been trying to see if Fedora's power management tool has something built
> in so that when the battery reaches full charge, it will then discharge
> to lets say around 95% before beginning to charge again. Friends of
> mine with the same laptop use such measures except they are running
> windows. However, based on the fact I did not see any documentation
> about this, and that my battery charge does not appear to fluctuate at
> all once it becomes fully charged (according to the statistics), I'm
> guessing no such thing exists in Fedora. Does anyone have any
> information as to whether this safety feature exists in Fedora, or
> whether some other measures exist instead? Basically I'm just wondering
> if I need to periodically unplug my laptop to preserve the lifespan of
> the battery, which would be annoying. Also if this is not a feature is
> anyone working on developing something like this for Fedora?
Charging of the battery is generally under firmware rather than software
control. Laptops will typically stop charging at 100%, at which point
the battery will slowly self-discharge. When the battery hits some
threshold (typically somewhere between 95% and 97%) the firmware will
start charging again.
What you're talking about is presumably an interface to modify that
threshold. This is device specific. The tp_smapi driver (which is not in
the kernel for exceedingly dull reasons) allows this to be configured on
Thinkpads. I don't believe that we know how to on any other systems.
--
Matthew Garrett | mjg59 at srcf.ucam.org
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