Though they don't specifically mention the location of the cmos battery.
If you do find it, the cmos battery type and spec will be mentioned on the battery.
Hmm, generally it would be under 'replacing coin cell battery' but I didn't find it either in the manual ... though generally the coin cell battery would be easy visible.
I have contacted Packerd Bell a few days ago. But no word from them. Perhaps they use a capaciter to store some energie. I don't know. But if so this means that if the main battery is empty the cmos will lose its configuration after some time.