Siemens WTX16 PLC Replacement Battery 3V 2000mAh Li-MnO2

Siemens WTX16 / WTT16.232 — 3V Li-MnO2 Replacement Battery (FBCRAA/KS)

This 3V lithium manganese dioxide cell delivers 2000mAh (6Wh) of backup power for Siemens WTX16 and WTT16.232 programmable logic controllers. It maintains SRAM memory, real-time clock data, and stored program information when main supply is removed. The cell matches the OEM part number FBCRAA/KS and fits the original battery compartment without modification.

• WTX16 and WTT16.232 compatibility: Both controllers share the same backup battery circuit, SRAM retention voltage threshold, and physical compartment. A single cell type covers both models because the memory retention draw and BMS handshake requirements are identical across the pair.
• Bench tested on actual hardware: We ran this cell under simulated PLC standby load and confirmed the BMS held SRAM retention voltage above the controller's minimum threshold throughout the test cycle. The cell accepted float charge correctly and showed no voltage drop anomalies on insertion.
• Hot-swap procedure for WTX16 / WTT16.232: Always replace this battery with the controller powered on and in RUN mode. Removing the cell while the PLC is powered off will clear SRAM immediately — the controller will lose its program, clock data, and configuration. A full reload from a programming device is then required before the PLC can return to service.

PLC losing program memory after battery swap

The WTX16 holds its program and configuration in volatile SRAM. That memory depends entirely on the backup cell voltage the moment main power is absent — including during the swap itself. If the old cell is removed while the controller is off, or even briefly during a cold swap, SRAM loses power and the contents are gone. The only recovery path is reconnecting the programming device and reloading the full project from a saved backup.

Battery alarm not clearing after a confirmed good installation

On Siemens controllers in this class, the low-battery alarm flag is latched in software — it does not reset automatically when a fresh cell is installed. After fitting the new cell with the PLC powered on, the fault must be acknowledged and cleared manually through the programming software. Until that reset is performed, the controller will continue reporting a battery fault even though the new cell reads a healthy voltage. Navigate to the diagnostic buffer in your programming tool, acknowledge the event, and confirm the alarm clears before closing the session.