[X4U] G4 Mac mini battery problem?

[Joe Sporleder]

I have a G4 Mac mini that was located at another office. It was  
running OS X 10.4.11. It was having trouble starting up (showing a  
folder/flashing question mark), any attempts to boot off another  
volume, DVD, Firewire, etc., failed. It is used primarily for  
Internet, Mail.app and Safari, plus a little bit in Pages and Numbers.  
I brought it back to my local office where I have my shop resources,  
and was finally able to get it to boot off a spare Leopard 10.5.3 DVD.  
So, I went ahead and upgraded it to Leopard, let it download all of  
the updates from Apple and got it up to 10.5.6. It worked fine for  
about a week or two under the new Leopard install, but now it has  
started doing the startup problem again, it'll either have the  
flashing folder/question mark as if it can't find a startup volume, or  
sometimes it won't even get that far, stalling at the grey startup  
screen, but before Apple's logo is displayed. Following the  
instructions for resetting the PMU on this model consistently fixes  
this problem, but the problem usually returns in a day or so. Is there  
a backup battery someplace that's dead that's causing this problem, or  
is the mini near the end of its life?

Joe