The battery IN or OUT has no direct function except to store the clock program data, and in some cases, the mem-batt program, if this program is executed.
You stated it had 1.5v at the battery. So, you do have a volt meter. How about the hard drive votages? -- Check the hard drive plug from the power supply.
The 2 center holes are ground, the yellow should be 12v.The other end should be 5v. The motherboard is powered by the same 5v. If you not getting these within .5v then your Power supply is weak or even worse if it's lower. Any electrically functional drive will spin, and seek. Just connect the drive, hold it in your hand, and power up. You will feel it's rotation.
If you have no hard drive attached, and the floppy drive worked, it can take several minutes for an A3000 to revert to the floppy boot up screen.
