I also have an 8300 and have experienced the same low cmos battery warning at start up. Dell insists there is nothing wrong with the battery and that it's caused by a ground issue when using some UPS systems. I did what they asked and that was to disconnect the computer from the UPS and plug it directly into the wall. That had no effect, so I plugged it back into my UPS. They asked why I didn't leave the computer on all the time, hardly a fix for the problem. I have 4 year in home so now I leave the computer on any time I'm home. The problem hasn't resurfaced but I feel that at some point the battery issue will reappear. If I were you, I'd contact Dell service before your warrenty period is over and get the battery issue on the record so you'll have recourse if it should totaly fail at some time in the future.

Issue is actually not with the UPS but with the surge protector. Some surge protectors, like the Belkin Surge Master powerstrip, have grounding protection which causes this issue.

I ddin't remember the exact cause but I have an large APC 650 and still had a bettery issue. Dell either has a bad stuck of CMOS batteries (which might come back to bite them down the line, because even corperations purchase 8300's ) or there's a design error causing all these failures. For the 2,000 plus dollars I paid for this computer the CMOS battery b/up shouldn't be an issue.

Thank you, everyone, for your responses. I contacted Dell and they are the ones who told me to change the voltage to match Germany's power. Even though my house has both the 110v and 220v, I changed over in the hopes that would solve my problem. No luck so far.

 I looked at the power management feature and found that the UPS was not enabled. I would like to try to configure that to see if it will help, but when I did try to use it, I had to choose from so many different version. I have no idea which one to choose, ie, Back-UPS or Back-UPS-Pro.

Thanks again for responding to my question.