Mazak 90041 PLC Replacement Battery 3V 5000mAh

Mazak MTN900 / QTN Series — 3V Li-MnO2 PLC Backup Battery (90041)

This 3V, 5000mAh lithium manganese dioxide cell replaces the PLC backup battery in Mazak MTN900, QTN100, QTN150, and QTN200 CNC control systems. It holds SRAM-stored machining programs and operational parameters during mains power loss. OEM part numbers covered include 90041, BBR-3, CR17450-2WK27, D80UB016170, and OV-204.

• MTN900 and QTN series compatibility: These Mazak controls share the same PLC memory backup circuit — same 3V supply rail, same physical footprint, and the same SRAM retention requirement. One cell spec covers all four models without modification.
• Bench tested on actual hardware: We ran this cell against the PLC float charge circuit and confirmed the BMS holds stable output across the retention voltage window. The cell accepts the trickle charge from the controller board without triggering an over-voltage cutoff.
• Hot-swap procedure for Mazak CNCs: Always replace this battery with the CNC controller powered on and in RUN mode. Removing the cell while the machine is off disconnects SRAM power instantly — stored programs and parameters are lost and will require a full reload from the programming device.

PLC losing program memory after battery swap on Mazak QTN controls

Mazak QTN and MTN900 controllers store machining programs in volatile SRAM. That memory depends entirely on continuous battery-backed voltage — even a two-second interruption during a cold swap wipes the contents. The PLC does not write programs to non-volatile storage by default on these platforms, so there is no automatic recovery. If the machine powered down during the swap, reconnect your programming device and reload the full program backup before attempting to run any cycle.

Battery alarm not clearing after fitting a confirmed good cell

On Mazak controls, the low-battery alarm flag is written to a status register — it does not clear automatically when a new cell is installed. The controller checks battery voltage at power-up and logs the fault, but it takes a manual acknowledgement in the ladder logic or diagnostic screen to reset the flag. Navigate to the PLC diagnostic or alarm history menu and clear the battery fault code directly. If the alarm reappears within 24 hours, verify the cell is seated fully and the connector is making clean contact — an intermittent connection reads as low voltage to the controller.