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Last night, while working on my Eee, I decided it was time to try some of the strategies for improving battery life that I've been reading about here on the forums.
So I turned my screen brightness down to 50%. Tried 30% to 40% as recommended, but my old eyeballs found that rather stressful. 50% seems fine though, at least under artifcial light.
I also turned off my wireless LAN, since I don't use it at home.
And guess what-- you guys were right! I don't have any hard data, but I started out the session with a 60% charge and was able to work much longer than I'd expected (at least an extra half hour, if not 45 minutes) before I got a low power warning.
Both these changes are extremely easy to make, even for a total newbie, by using the function keys.
Any other super easy power saving tips?
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really, brightness and wifi are the only killers of battery life in the eee.
you could also clock-down the cpu to save power.
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How much power does disabling the wired ethernet save? Can anybody share?
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Newsguy wrote:
How much power does disabling the wired ethernet save? Can anybody share?
answer: more than you would think.
WiFi requires LOTS of battery life and I can gaurentee loses you a large amount of battery life.
if your just typing, you could downclock to around 630 mhx, a reasonable amount of power for word processing. that would give you additional time.
If you're really concerned, buy the 6-cell battery accessory that ASUS sells now.
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Paul wrote:
Newsguy wrote:
How much power does disabling the wired ethernet save? Can anybody share?
answer: more than you would think.
WiFi requires LOTS of battery life and I can gaurentee loses you a large amount of battery life.
if your just typing, you could downclock to around 630 mhx, a reasonable amount of power for word processing. that would give you additional time.
Disabling WiFi, as you say saves quite a bit of power.
Disabling the Wired ethernet port will save some, but not much. From experience on embedded boards possible around 0.2W.
Instead of manually altering the cpu clocking speed, why not use one fo the variable governors in the kernel.
The ondemand one selects an appropriate cpu clock speed to match the load - ranging from a claimed 100 to 800Mhz on my 2G SURF. Check out the /usr/sbin/services.sh script.
Make sure the relevant lines are enabled.....
modprobe p4_clockmod
modprobe cpufreq_ondemand
echo "ondemand" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
chmod 644 /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
to find out what your current CPU clocking is do
cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
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I'm not really all that worried-- not enough to mess with my clocking. The hassle of changing it and then changing it back whenever I want to play games or go online ... It's interesting though, and I'll try to remember the thread is here if I ever want to try it. I've heard of overclocking before, but never of underclocking.
Right now, I'm just being "as green as I can" and trying to ensure the maximum number of finished thoughts and games of freecell between charges until I can get my hands on that six cell battery!
Last edited by yardcoyote (2008-01-10 5:36:17 pm)
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Good call on the brightness. I may or may not have thought of that, so it's nice to see it posted as I was looking round!
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how do u change the brightness? sowwwie if its a dumb question...im new myself....
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Yay! The Yardcoyote, who was a total newb two weeks ago, can answer a question! (It's not dumb-- I learned it yesterday from Help ...)
To turn the brightness down, hold down the Fn key and press F3.
To turn it back up again, hold down the Fn key and press F4.
In both cases, a handy little slider will appear to show your brightness status.
Last edited by yardcoyote (2008-01-10 8:35:46 pm)
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in my opinion, the two battery killers on the eee are brightness and wifi, anything else will save a little, but not much.
a little thought, lower the time it allows for going into screensaver and powering off the monitor, turning both down will help (like on my ipod)
if those two changes don't do it you need a larger battery.
EDIT:
jeez my typing is teeerible.
Last edited by Paul (2008-01-10 10:50:24 pm)
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In my experience, WiFi isn't terrible, unless downloading a lot of files on it. Reading forums most nights from the comfort of the couch for about 2-2 1/2 hours, and usually have 30-40% charge when I go to shut it down.
Another trick about the backlight - turn down lights in the room you are in. The lower the background level of light, the lower you will need the backlight.
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IF you DO need wifi you can lower the radio's transmit power to save you a little juice.
I took mine down from 100mw (default) to just 5mw, and I still get full bars and flawless connectivity (my wifi router is rather central in my home, and the signal easily reaches everywhere I need to be).
Nice thing is that with the Atheros util in XP I can change the power on a case by case basis - like if I needed ti to have more power at the office I can set it so, and each profile remembers it's setting when I switch.
(Atheros client util ->profile management -> modify -> advanced -> transmit power level)
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Nate wrote:
IF you DO need wifi you can lower the radio's transmit power to save you a little juice.
How do I do that in Xandros?
Last edited by nick1austin (2008-01-11 6:10:27 am)
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nick1austin wrote:
Nate wrote:
IF you DO need wifi you can lower the radio's transmit power to save you a little juice.
How do I do that in Xandros?
Not sure, I only used the stock install for a few hours before Nuking it for XP, but *BUMP* all the same so hopefully one of the more experienced Xandros users can help...
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Just as a general note there is a website by Intel specifically on power saving on Linux
http://www.lesswatts.org/tips/
A warning though, some tips require certain kernel versions and configurations. Xandros uses an older kernel so a lot of them won't apply. Also they are not exactly walkthroughs, and 'may' require a bit of linux know how to understand them properly. Only try them if you know what you're doing.
@Paul: There have been vast strides that have been made in the Linux kernel over the past year in regards to powersaving (more than just wifi and screen brightness 
). Unfortunately, due to the old kernel in Xandros, a lot of the new code is not present. The main one that can easily be implemented is the ondemand governor mentioned above (although you don't have an eee ). Also unfortunate is that I don't have an eee to play around with the power savings capabilities (it is a hobby of mine, minimising cpu wakeups). If I'm simply browsing web pages or writing documents, I can squeeze about twice the battery life out of my laptop by using power saving techniques, haven't done a full test, just based on the battery time remaining (and that ain't including turing wifi off, as it was already off). Obviously the savings are reduced if you watching dvds or compiling programs (cpu intensive). The only noticable difference it makes is that it takes a second or so to power up the harddrive if I leave it for 20 minutes. Based on the power consumptions recorded in other threads, I'm quite sure that my 14.1" laptop uses less power than the eee does (even with all the extras it has).
I'd love to see how many hours I could get out of an eee!!!
P.S. I'm no greenie
Last edited by Vandy (2008-01-12 7:20:49 am)
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Thanks for the hint that it was possible, I've done some searching and found the xandros method.
To set the power, bring up a command window (ctrl-alt-T) and type:
sudo iwconfig ath0 txpower 2mW
To see the statistics:
/home/user> sudo iwconfig ath0
Warning: Driver for device ath0 has been compiled with version 22
of Wireless Extension, while this program supports up to version 20.
Some things may be broken...
ath0 IEEE 802.11g ESSID:"XXXXXX" Nickname:""
Mode:Managed Frequency:2.412 GHz Access Point: 00:18:4D:FE:95:1C
Bit Rate:48 Mb/s Tx-Power=4 dBm Sensitivity=0/3
Retry:off RTS thr:off Fragment thr:off
Encryption key: [snipped] Security mode:restricted
Power Management:off
Link Quality=27/94 Signal level=-68 dBm Noise level=-95 dBm
Rx invalid nwid:1607 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0I think I had it working at 1mW, but then the Tx-Power statistic read "off", which is probably lying, but I'd rather be safe. Note the "Tx excessive retries" at the bottom is probably where you'll see if you've got it too low.
dBm is decibels over 1mW:
1dBm = 1mW,
3dBm = 2mW
7dBm = 5mW
10dBm = 10mW
13dBm = 20mW
17dBm = 50mW
This probably needs doing on every reboot, but maybe someone will tell us where to put it, to have it done automatically.
Editedx3 to add new stuff.
Last edited by rurwin (2008-01-12 9:00:59 am)
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have dimmed the screen and have got an notable increase in battery life, thanks guys
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I have had my eee for about a week and am totally impressed in all respects. One minor gripe is the battery power, it would appear that I get at best 3 hours of use. (more likely 2.5 hours) This is somewhat disappointing considering what is being drawn from it.
I have tried all of the tweaks as suggested on this forum, I struggle to use the screen comfortably at less than 40%. I have disabled the webcam in the BIOS as I would rarely use it, I usually leave the WIFI on as this is my main use with the eee.
Other than that I doubt if it can be tweaked anymore to extend the battery life. I would be interested in the 7800mAh batter when it becomes available, mind you, if it is £58.75 (Inc VAT) I might just struggle along.
I travel alot on business and this little machine will be invaluable to me. My typical usage when away is for emails and reports therefore should fit the bill perfectly. I have installed XP Home SP2 and this makes it the ideal business companion.
This forum has been particularly useful for sorting queries out, many useful contributions. Is Neil full time? He seems to be available to everyone with amazing knowledge and willingness.
Tewy
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Tewy wrote:
it would appear that I get at best 3 hours of use. (more likely 2.5 hours) This
thats good! thats what its advertized as
Tewy wrote:
I have tried all of the tweaks as suggested on this forum
so you didn't want to try underclocking then?
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I'm waiting for the larger battery as well. A spare charger would be useful also.
Last edited by agni (2008-01-14 4:42:07 pm)
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agni wrote:
I'm waiting for the larger battery as well. A spare charger would be useful also.
has the battery not already been released? or is it not sold near you yet...
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Re: underclocking to save power, I did some tests with Eeeclock, and it didn't make a difference at idle. The Eee's already running at a reduced voltage, even at the stock speed.
Bumping voltage for overclocking will raise idle consumption. Otherwise, speed's not a factor.
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geoelectric wrote:
Re: underclocking to save power, I did some tests with Eeeclock, and it didn't make a difference at idle. The Eee's already running at a reduced voltage, even at the stock speed.
Bumping voltage for overclocking will raise idle consumption. Otherwise, speed's not a factor.
hrm, I guess thats not much of a power saver.
what parts of the eee get really hot? just the cpu? getting the eee in a heat free enviornment would result in a faster and more powerefficent eee pc!
Last edited by Paul (2008-01-14 5:28:21 pm)
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I took rurwin's idea about lowering the wifi transmit power, and wrote a small script I called Low_power_wifi, for which I have an icon in full desktop. It toggles the power down to 2mw, and also reports the cpu temperature (just because). If you click on it again, it restores full power. It is a little clumsy in how it does string comparisons, because I'm just learning. I'm sure it could be made more elegant.
I put in in as /usr/sbin/Low_power_wifi and then gave the command chmod +x /usr/sbin/Low_power_wifi
Then I created an icon link to activate it with a click, so it's easy to lower wifi power used if on battery.
----------------------------------------------
#!/bin/bash
s=`sudo iwconfig ath0 | grep "Tx-Power"`
LOW_WIFI=${s:37:5}
if [[ $LOW_WIFI = "=4 dB" ]]
then
sudo iwconfig ath0 txpower 100mW
s=`sudo iwlist ath0 txpower | grep "Current Tx-Power"`
t=`cat /proc/acpi/thermal_zone/TZ00/temperature | grep "temperature"`
kdialog --msgbox "Full Wifi Power Restored:
$s $t"
else
sudo iwconfig ath0 txpower 2mw
s=`sudo iwlist ath0 txpower | grep "Current Tx-Power"`
t=`cat /proc/acpi/thermal_zone/TZ00/temperature | grep "temperature"`
kdialog --msgbox "Lower Wifi Power Set:
$s $t"
fi
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Sorry if its a bit off topic, but is it possible to raise the wifi power if you aren't worried about battery life?
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