I am restoring an Atari STacy, and it is a notoriously hard device to open — I am planning to replace the floppy drive and internal CMOS battery in one go... but while I know the floppy is an Epson SMD 380, I do not know the exact spec of the battery.

I would rather not open the machine and leave it half-assembled for a week. Anyone have a tip on the battery type?

I found this picture of the STacy's innards: enter image description here

  • 2
    Your image from Atari Stacy computer has a third-party expansion board obscuring the battery and appears to have a Li–SOCl2 battery of its own
    – scruss
    Commented Apr 16, 2022 at 19:54
  • Oh. I have not seen the inside of mine so I did not realize that was the case. Thanks!
    – 0xF2
    Commented Apr 17, 2022 at 13:55
  • Updated with better, not-obscured picture.
    – 0xF2
    Commented Apr 17, 2022 at 14:03
  • 1
    Just for clarification, while the battery in older systems uses to feed a NVRAM it is near always an indicator the system has a RTC; while you could replace the original persistent RAM with more modern NVRAM such as flash, the real time clock system needs to be always powered. I am not used to the STacy, but if there was some sort of relatively large cavity easily accessible from the outside (such an unused expansion slot) I would recommend to add an AA battery carrier to ease future replacements.
    – Borg Drone
    Commented Dec 7, 2022 at 11:55

1 Answer 1


The Stacy is essential a Mega-ST. The battery used is a standard 3 volt CR2354 cell ... except with soldering wires welded on. Panasonic offers them in various configurations, the 90 degree version CR-2354/HFN might work with the Stacy. Note, there are different versions with wide and small soldering stripes. I can't tell which one goes with the Stacy without opening mine.

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