Power Management

[Hans Ulrich Niedermann]

Matthew Garrett wrote:
> On Mon, Feb 16, 2009 at 07:02:52PM -0500, brad longo wrote:

> 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.

I have been running tp_smapi locally for quite some time to reduce the
number of charge cycles on my battery and thus its lifetime.

Given that kernel modules are a no-go in Fedora and I remember having
read somewhere that most of the code is to be expected to go into 2.6.29
or something similar, I have not published my packages until now.

However, someone still might find them useful:

    http://ndim.fedorapeople.org/packages/tp_smapi-kmod/
    http://ndim.fedorapeople.org/packages/tp_smapi/
  or
    git://fedorapeople.org/~ndim/tp_smapi-kmod-package.git
    git://fedorapeople.org/~ndim/tp_smapi-package.git

These tp_smapi* packages require the rpmfusion akmod stuff.

The user interface is a file in /etc/sysconfig with the two threshold
values. I use 40% as start-charging threshold and 80% as stop-charging
threshold. Occasionally when I know I need more capacity on the road, I
manually force it to start charging and charge higher.

Eventually, I'd like to see that functionality in Fedora with a nice
user interface, but right now it works for me, so I can live with that.

-- 
Hans Ulrich Niedermann