Replace the original 5101 NVRAM chip.
No batttery needed anymore, the used F-RAM chip stores NVRAM data without a battery backup.
I have created two versions.
Version1 supports pinball MPUs which need dual CE ( like Gottlieb system80 or Williams SYS3 & SYS4 )
Version2 supports pinball MPUs which need dual CE and use seperate pins for input/output ( like Gottlieb system1 or Atari). Version2 works also in systems where version1 works.
Note: both versions will work also on pinball MPUs with 5101 NVRAM which do not have special requirements for 'dual CE' or seperate in/out. ( e.g. Bally MPU )