GE FANUC 16i PLC Replacement Battery 3V 2000mAh Li-MnO2

GE FANUC 16i / 18i / 21i Series — 3V Li-MnO2 Replacement Battery (A98L-0031-0012)

This 3V lithium-manganese dioxide cell replaces the CMOS memory backup battery in FANUC 16i, 18i, 21i, and Power Mate iD CNC controllers. It maintains SRAM contents — stored programs, tool offsets, machine parameters, and the real-time clock — during mains power loss. Capacity is 2000mAh (6Wh), matching the OEM specification for A98L-0031-0012 and A02B-0200-K102.

• FANUC 16i / 18i / 21i compatibility: These controllers share the same battery compartment footprint and SRAM backup circuit. The cell sits on a float rail — no BMS handshake is required, but the connector and cell geometry must match to maintain contact pressure against the PCB terminal.
• Bench tested on actual hardware: We loaded this cell into a FANUC 16i-MB and confirmed stable SRAM retention voltage above 2.8V across simulated mains-off cycles. Open-circuit voltage on fresh cells measured 3.0–3.1V before installation.
• Hot-swap procedure for FANUC controllers: Always replace this battery with the CNC controller fully powered on and in RUN mode. Removing the cell while the controller is off erases SRAM instantly — stored programs, parameters, and offsets are gone. A cold swap means a full program reload from the programming terminal before the machine can run.

Why the FANUC 16i loses all parameters after a battery swap

FANUC 16i and 18i controllers use static RAM with no internal capacitor buffer. The moment battery voltage drops below the SRAM retention threshold — typically around 2.5V — all contents are lost. Unlike some PLCs, FANUC's memory circuit does not hold data for even a few seconds without power. If the swap was done cold, the controller will boot into an alarm state and request a parameter reload. Restoring from a CNC data backup file loaded via RS-232 or CF card is the only recovery path.

BAT alarm still showing after fitting a confirmed good cell

On FANUC Series 16i and 18i, the BAT alarm does not clear automatically when a new cell is installed. The alarm latch must be manually reset through the MDI panel or FANUC LADDER-III software after the new battery is seated and the controller confirms voltage above threshold. Leaving the alarm uncleared does not affect machine operation, but it masks any future genuine low-battery warning. After fitting the new cell, navigate to the diagnostic alarm screen and perform a manual alarm reset to confirm the flag clears.