how to set battery thresholds?

[kvaso]

hi
I've got SL500 and I wonder how to set battery thresholds.. Power manager help says:

To change the battery charge thresholds, click the Battery Maintenance... button on the Battery Information tab etc

but here is, how my Power manager looks like: http://img198.imageshack.us/img198/344/65445584.png

could you help me how to solve this problem?
thanks a lot