Weak Battery Life

[Dat]

I've noticed that my battery life is less than half when I ran it on Vista. Does anyone else notice a weaker battery life using Kubuntu?

[olembe]

Re: Weak Battery Life

Hi,

Yes, I have found something similar. I run Kubuntu on my Macbook Pro and get much lower battery life. To some extent it's to be expected: Vista and Mac OS X have lots of tweaks to get as much battery life out of a laptop as possible, and most versions of Linux tend not to have this.

The best tip I got was to download Powertop (type "sudo apt-get install powertop" (without quotes) in a terminal window). When you run this (type "powertop" in a terminal once it's installed) it will show you which programs are causing the biggest drain on your battery and give you tips for turning off processes which are using power - for example, it usually offers to shut down your unused webcam, stop the computer continually checking your CD-ROM drive, allow USB ports to be automatically suspended, etc. Just accept all the suggestions it offers and that should give you quite a boost to your battery. The downside is you need to run Powertop again each time you've restarted your computer.

On the other hand, once you're familiar with the options Powertop adjusts (CD-ROM polling, dirty writeback time, etc.) you can permanently adjust these settings to increase battery life. Go to the directory /etc/laptop-mode/conf.d/ and look inside the various files there with a text editor such as kate. You can edit each file in this directory and turn on whichever option it offers. It's quite self-explanatory. For example, edit /etc/laptop-mode/conf.d/usb-autosuspend.conf and there is a clear line saying:

# Enable USB autosuspend feature?
CONTROL_USB_AUTOSUSPEND=0

Change the 0 to a 1 and from then on, when you're working on battery your USB system can automatically go into suspend mode.

All this relies on your computer having laptop mode enabled. You can check this by looking at the file /etc/default/acpi-support which contains the line:

ENABLE_LAPTOP_MODE=true

If yours reads 'false' then changing it to 'true' will allow your computer to use laptop mode and so allow any changes you make to the /etc/laptop-mode/conf.d/ files to operate.

I hope I haven't made this too complex: do say if you want clarification of anything.

[GreyGeek]

Re: Weak Battery Life

If batteries are kept charged to 100% they have shorter lives. Both VISTA and Kubuntu (at least on my Sony VAIO VGN FW140E) set the max charge at 80%.

[bitnissen]

Re: Weak Battery Life

If batteries are kept charged to 100% they have shorter lives. Both VISTA and Kubuntu (at least on my Sony VAIO VGN FW140E) set the max charge at 80%.

Did you have to activate this yourself or is it just done automagically? It is not so on my Lenovo X61s, and I have not found a way to activate it - thats why Im asking

[toad]

Re: Weak Battery Life

ditto - how did you manage that, greygeek? Please share the secret

[GreyGeek]

Re: Weak Battery Life

ditto - how did you manage that, greygeek? Please share the secret

On my Sony VAIO VGN-FW140E it was set using the VISTA via the "BatteryCare Function" under the VAIO Control Center, which setting the Kubuntu PowerManagement applet honors. (At first I thought I had set it under the BIOS, but I realized that I had never accessed the BIOS on this laptop.)

[toad]

Re: Weak Battery Life

Hm, neither having a sony nor vista I reckon the last port of call would be the BIOS. I remember something odd in there but nothing like that. Must either investigate or remove my battery when it is time as I have always done Ah, the good old days...

[GreyGeek]

Re: Weak Battery Life

I googled for "Battery Care Function" and found some interesting information. This "problem" was originally posted as a bug: https://bugs.launchpad.net/ubuntu/+s...ux/+bug/177963

But, after some investigation, they discovered it wasn't a bug.

Michael Doube wrote on 2007-12-30: (permalink)

Hmmm. Looks like the smart battery is a bit too smart. Sony's "Battery Care Function" (running in Windows to prolong the battery's service life) caps the maximum charge that the battery will take before reporting that it has finished charging. The battery then remembers this amount (50%, 80% or 100%) and carries it over to Linux, which gets the maximum charge from /proc/acpi/battery/BAT1/info and compares it to the charge when finished charging in /proc/acpi/battery/BAT1/state and (correctly!) calculates 80% of maximum charge. So I guess the way around this is either to disable the feature in Windows, or emulate the maximum charge setting in Linux somehow.

My "/etc/acpi/battery/BAT0/BAT0 gave:

jerry@jerry-sonylaptop:~$ cat /proc/acpi/battery/BAT0/info
present: yes
design capacity: 50610 mWh
last full capacity: 50610 mWh
battery technology: non-rechargeable
design voltage: 118690 mV
design capacity warning: 1000 mWh
design capacity low: 400 mWh
capacity granularity 1: 100 mWh
capacity granularity 2: 100 mWh
model number:
serial number:
battery type: LiOn
OEM info: Sony Corp.

I checked the specs for my VGP-BPS13/S battery:
Volts: 11.1v (proc shows 11.8v)
mAh: 4,400 mAh (computed at 4,264 mAh)
mWh: 48,810 mWh (proc shows 50,610 mWh)

My mWh is 3.6% greater than specs show. Don't know why.


My "cat /proc/acpi/battery/BAT0/state" gave:

jerry@jerry-sonylaptop:~$ cat /proc/acpi/battery/BAT0/state
present: yes
capacity state: ok
charging state: discharging
present rate: 19440 mW
remaining capacity: 40490 mWh
present voltage: unknown

BUT, "remaining capacity" is 80% of "design capacity", as the bug report indicates!!!

I have used the battery several times and each time, when it recharges, it does so only to 80%. What "PowerManagement" is using as a guage to determine when to turn off the charging I don't know, but "remaining capacity" could be one item. During recharge, when it reaches 80% of "design capacity", the charging shuts off.

Interestingly, "present rate" seems to indicate how many watts my laptop is consuming at the present.

[stimpyjcat]

Re: Weak Battery Life

look at the power management profiles to check if they are not messed up (i have modified the powersave and the profile assignment to my notebook)

[kevinc]

Re: Weak Battery Life

Weak battery life must be one of the few remaining issues before Linux overtakes Windows in every way. Of course Linux is already way ahead in security, speed, reliability and many other areas.

My HP notebook has two batteries; one normal and one travel. With the original windows it was getting up to eight hours on a full charge. With Debian Etch it was down to 2.5 hours and with the Feisty, Hardy, Intrepid and now Jaunty each time the maximum is less. Of course the machine is three years old next month and gets used at least eight or more hours each day, usually getting fully charged and emptied once each day. The current limit is just on one hour, so now I have to take the transformer to plug it in when I take it to the internet cafe.

[GreyGeek]

Re: Weak Battery Life

Three years old, and fully charged and discharged each day? The current length of service of your charged battery has less to do with Linux than it does with wearing out.


http://www.batteryuniversity.com/parttwo-34.htm

Aging of lithium-ion is an issue that is often ignored. A lithium-ion battery in use typically lasts between 2-3 years. The capacity loss manifests itself in increased internal resistance caused by oxidation. Eventually, the cell resistance reaches a point where the pack can no longer deliver the stored energy although the battery may still have ample charge. For this reason, an aged battery can be kept longer in applications that draw low current as opposed to a function that demands heavy loads. Increasing internal resistance with cycle life and age is typical for cobalt-based lithium-ion, a system that is used for cell phones, cameras and laptops because of high energy density. The lower energy dense manganese-based lithium-ion, also known as spinel, maintains the internal resistance through its life but loses capacity due to chemical decompositions. Spinel is primarily used for power tools.

The speed by which lithium-ion ages is governed by temperature and state-of-charge. The attached graphic illustrates the capacity loss as a function of these two parameters.

Graphic: Permanent capacity loss of lithium-ion as a function of temperature and charge level.
High charge levels and elevated temperatures hasten permanent capacity loss. Improvements in chemistry have increased the storage performance of lithium-ion batteries.

[toad]

Re: Weak Battery Life

I've got an IBM T41 and a 6600 mA battery which lasts some six hours. I wouldn't know what it is capable of under M$. I've been taking good care of the year old thing, removing it when charged. To get the most of it I use powertop and dim the display. Under KDE3 it was up to 8 hours (might also have been 'cos it was younger then...).

[kevinc]

Re: Weak Battery Life

Thanks GreyGeek. My HP batteries have been well used and their shorter life now is due to the oxidation over three years.

When new, under windows, for the first six months under windows the average use on a full charge was 8 hours. Once I had Linux installed the total life was reduced to under four hours and within a short time to three hours. I have no intention of using windows again, but I use another older Toshiba notebook with an 8000mAhr battery and it still gets over four hours on a full charge and takes just as long to charge it again.

There's not a lot that can be done about temperature for those who live in hot places with no power apart from keeping everything in the coolest place available.