have a couple of old Mac portables and they seem to be
real power hogs.
(That's probably why they use lead acid batteries instead of NiCads.) My
small HP power supply won't run them. Even with the drives off, it will
only run them with a partially charged battery to take up some of the peak
load. It won't run at all when the batteries are dead. And forget it when
the drive kicks in!
I have a bunch of Apple powerbook adapters, and generally if you use the
larger of the 1xx series adapters that will run the portable including
spinning up the HD, but just barely. Any battery "problems" and it won't
spin up without resetting the computer. I have 3 batteries to play with,
and at least one will hold a partial charge, but I really don't want to
fiddle with the battery every couple years.
Something to play with anyway.