install Debian instead, same thing after a few changed settings and upgraded packages, just use testing instead of stabel (not as unstable as it sounds).

but if you persist with installing Knoppix I would suggest NOT to upgrade it, it WILL break, and when it does you are more or less on your own.
I will TRY to help but I have Debian so I have to guess some as to your install...

firstly, there was a bug in acpi (a monitoring tool that does the power saving, battery monitoring, fans...) that was affecting battery monitors, it showed just 100% until battery was so low it shut computer down, sounds like you have that faulty version.

second as long as you have power plug in it will run 100% all the time almost no matter what setting you use.
as for the screen blanking, have you checked screen saver settings? they can blank the screen if set to do so, and are not always affected by kpowersave settings.

the above is main reason I never use tools like this, I edit the configuration files, I then know what is done and where, true it takes a while to find the right firle/s under the /etc directory, but not too much so.