Ubuntu – How to disable asus-nb-wmi when using battery power mode

I'm trying to improve the battery life of my Asus U32U notebook. I'm running Ubuntu 12.04 64bit and using powertop it shows the following:

PowerTOP 1.97     Overview   Idle stats   Frequency stats   Device stats   Tunables   

Summary: 311.6 wakeups/second,  0.0 GPU ops/second and 0.0 VFS ops/sec

Power est.      Usage       Events/s    Category       Description
  6.29 W    100.0%                      Device         Radio device: asus-nb-wmi
  1.19 W    100.0%                      Device         Display backlight
    0 mW     49.3 ms/s      42.8        Process        compiz
    0 mW     19.5 ms/s      51.4        Process        /usr/bin/X :0 -auth /var/run/li
    0 mW     10.3 ms/s      16.8        Process        gnome-terminal
    0 mW      5.5 ms/s     118.1        Interrupt      PS/2 Touchpad / Keyboard / Mous
    0 mW      2.0 ms/s      37.0        Interrupt      [45] fglrx[0]@PCI:0:1:0
    0 mW      1.6 ms/s       0.4        Process        powertop
    0 mW      1.5 ms/s       1.1        Process        /usr/lib/unity/unity-panel-serv
    0 mW      1.0 ms/s       4.5        Timer          tick_sched_timer
    0 mW      1.0 ms/s       9.3        Process        syndaemon -i 2.0 -K -R -t
    0 mW      0.9 ms/s      20.3        Timer          hrtimer_wakeup
    0 mW      0.8 ms/s       0.2        Process        [flush-ecryptfs-]
    0 mW      0.7 ms/s       0.9        Process        /usr/lib/gnome-settings-daemon/
    0 mW    697.3 µs/s       0.2        kWork          rfkill_poll

According to this Ubuntu community help page the asus-nb-wmi driver is responsible for implementing the function keys, something I can definitely live without if it means I will get longer battery sessions.

So I would like to know if its possible to disable the asus-nb-wmi when not plugged in to AC power, and if so, how.