Fit a remote battery holder

Steps

• Use an AA holder mounted away from the board; a 4-cell holder with a 1N4001 diode in series works well, and the diode makes the low battery prompt appear before the cells start to leak.
• Solder the red lead to the original battery holder positive pad on the CPU board, not to the B+ or VBAT test point, which is after the blocking diode.
• The black lead can go to the NEG test point.
• Check between B+ (or VBAT) and NEG: above 4 V, a little lower than at the holder because of the diode(s).

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• Replacement battery holder for the CPU board
• Updating pre-Ice Fever reset boards to protect RAM Z5
• A single lamp does not light
• Repairing battery corrosion on the CPU board
• Check that battery power reaches the RAM at 5D
• Repair battery corrosion on the CPU board
• "Memory Error, Open Door" or "open the coin door" at power-on
• Change the CPU backup batteries yearly, with the game on

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Three, Clay Harrell (pinrepair.com)