Saving power on my laptop I

I’m using an Acer TravelMate 4672WLMi at home and I was never happy with the lifetime of the battery. About 2 hours is the most I get out of it. So I’m trying to tweak Ubuntu (just upgraded to 7.10) a bit to see what can be done. I got the inspiration from http://www.lesswatts.org/ – so full credit to those boys and girls!

The first thing I wanted to do is to reduce the power consumption of the wireless card. You usually do this by calling ‘iwpriv eth1 set_power 5’ to enable the power-saving mode. However, I wanted an easier way without having to run this command manually whenever I’m not connected to the mains.

So I had a look around in /etc to see if I could find anything that could help. Here I came across a directory called laptop-mode which belongs to a package of the same name. Here I found a subdirectory conf.d/wireless-ipw-power.conf. This file consists of only one line (apart from a few comments):

CONTROL_IPW_POWER=0

That looked exactly what I needed. I changed that value to 1 and restarted the laptop-mode by running:

sudo /etc/init.d/laptop-mode restart

Unfortunately that didn’t have any effect as iwconfig indicated that the power saving for the wireless card was still disabled. However, I very quickly noted by running ‘sudo laptop_mode’ that the laptop mode wasn’t enabled at all:

$ sudo laptop_mode
Laptop mode disabled, active.

After a quick look in the /etc/init.d/laptop-mode I learned that I had to enable the laptop mode by setting ENABLE_LAPTOP_MODE to true in /etc/default/acpi-support (read the warning in the associated comment as well!). After this was done and another call of

sudo /etc/init.d/laptop-mode restart

the power saving for the wireless card was enabled. Seems to save a ‘massive’ 50mA. Happy days!

Of course, that’s not the end of it and more options will need to be tweaked to save more power. Why is nothing easy with Linux 😉 ?

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