System cannot set to shutdown when battery in critical level

Hi guys,

I faced a problem which is set the critical action as shutdown and it did not work when battery is in critical level.
I tested in SLED 11 SP2 with below configuration.

>gconf-editor

Set the setting under gnome-power-manager as below,

apps/gnome-power-manager/actions:
-critical_battery = shutdown
apps/gnome-power-manager/general:
-use_time_for_policy = false
apps/gnome-power-manager/thresholds:
-percentage_action = 0
-percentage_critical = 10
-percentage_low = 30

I have checked that it is working when -percentage_action set as 10. But it is
not working when set as 0.
I will like to set the critical action as shutdown when battery reach 0% .
The percentage_action is not working when set as 0?
What is the minimum value it can be set ?