Just as a followup here, my Mac Portable (no backlight) runs just fine without a battery. I use a regulated 9V 3A power supply connected to the rear power adaptor. This is enough to get the original Conner drive up and start the machine. Lower than that and it will flip out. I dug it out of the closet since it was a little wonky and did some work on it, and it still works fine.

http://www.floodgap.com/iv/1759