power problem


hi all
first time here
I have a G4 powermac that is acting strangely
It switches itself off for no apparent reason it can be on for a whole day or 10 minutes somtimes it wont power up at all when it does the clock and date has reset itself,
I know that is related to the motherboard and battery but i checked the battery and its fine any help i´m puzzled :confused:
Whether or not you are the original owner - how old is the Mac?
Providing a specific Mac model (MacTracker) would help.

When was the last time the battery was replaced?

And just how did you check the battery? Under load (still plugged in) or non-loaded (removed from the Mac) - with a voltmeter? Look at this Apple web page.