Saft LS14250 C lithium issue?

Thanks. The G5 is late enough that a dead battery is unlikely to cause a boot issue. That pretty much affected what Apple called "Old World ROM" models--basically any PowerMac older than the Blue & White G3.

Still, replacing a PRAM battery is often a cheap diagnostic. So is booting from a bootable optical disk. Even in the Old World ROM days, a Mac with a stone-dead PRAM battery would cold-boot from a system CD or DVD and a subsequent warm boot from the hard drive would give you a working computer until the next time you shut it down.

What concerns me is that I am starting to see more power supply problems with G5 tower models. Late last year I searched for sites that had diagnostic info on the G5 power supplies but most were about G5 iMacs, not PowerMacs. If you search, try the string, "powermac G5 pinouts" as well as "powermac G5 power supply service."

Some Macs won't start up if the PRAM battery is dead. (This is a non-rechargeable lithium button cell.) You should get it replaced by an authorised Service engineer.

Exactly what PowerMac model do you have? Newer ones are not as susceptible to the "dead battery--won't boot" issue as the older ones.