HowTO: Fix Laptop Battery not Detected in LXDE Applet

Although it is really the fault of the application having a certain location hard coded into them, one way to workaround a problem with the battery not being detected by the battery applet.

First though, to confirm that this fix applies to you, run the following:

ls /proc/acpi/battery

If you get something other than CMB0 in the output, this fix may not apply to you.

First thing we need to do is install the iasl compiler/decompiler

sudo apt-get install iasl

Then obtain a copy of your motherboard’s dsdt

sudo cat /proc/acpi/dsdt > dsdt.dat

Decompile the dsdt

iasl -d dsdt.dat

Then change all instances of CMB0 with BAT0 using sed

sed -i 's/CMB0/BAT0/g' dsdt.ds

and finally compile the dsdt again

iasl -tc dsdt.dsl

You may receive errors/warnings when compiling. If your system runs just fine, you can safely ignore these, else you may want to look into fixing them, as a buggy dsdt can mean that you are unable to suspend/hibernate.

To implement the new dsdt into your system, run the following:

sudo cp dsdt.aml /etc/initramfs-tools/DSDT.aml
sudo update-initramfs -u all

and then just reboot.

To test that dsdt is working, run the following:

ls /proc/acpi/battery

and you will now see BAT0 in the output.

Note: The Kernel Devs will no longer use the patch to enable custom DSDTs for all releases after Karmic. Jaunty will be the last release that this works on.