Allen Bradley 1770-XYC PLC-5/11 Replacement Battery 3V 2200mAh

Allen Bradley PLC-5/11 Series — 3V Li-MnO2 Replacement Battery (1770-XYC)

This is a 3V lithium-manganese dioxide cell rated at 2200mAh (6.6Wh), built to the 1770-XYC spec. It fits the Allen Bradley PLC-5/11, PLC-5/20, PLC-5/30, PLC-5/40, and more than 40 additional PLC-5 series processor modules. Its sole job is to hold SRAM program data and the real-time clock when main power is removed.

• PLC-5 series compatibility: The PLC-5/11 through PLC-5/40 and related modules all use the same 3V backup cell on the same memory-retention rail. The 1770-XYC footprint and connector are consistent across the line, so one cell covers the full platform without modification.
• Bench tested on actual hardware: We ran this cell against the 1770-XYC spec on the bench and confirmed the BMS holds the SRAM retention voltage above the 2.5V cutoff threshold. The cell maintained stable output under low-drain standby conditions across the full test window.
• Hot-swap procedure — critical for PLC-5 modules: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is de-energised wipes SRAM instantly. If the PLC was off during the swap, a full program reload from the programming terminal is required before the controller will operate correctly.

SRAM retention voltage threshold on the PLC-5 processor module

The PLC-5 processor uses static RAM that requires a minimum of approximately 2.5V at the backup rail to retain data. A fresh 1770-XYC cell ships at storage voltage — typically 2.9V to 3.0V — and rises to its full rated output within a few hours once seated on the processor's float charge circuit. Below the 2.5V threshold, the SRAM loses its charge and all ladder logic, data tables, and RTC values are erased. Monitoring the battery alarm output in RSLogix 5 gives you the earliest warning before the cell crosses that threshold.

PLC-5 battery alarm still active after installing a confirmed good cell

The PLC-5 does not automatically clear the battery fault status when a new cell is seated. The alarm flag is latched in the processor status file and must be manually reset through the programming software — typically by clearing the battery low bit in the S:11 status word in RSLogix 5. If the bit is not cleared, the controller continues to report a battery fault regardless of cell condition. After clearing the bit, verify the processor status file shows the flag at 0 before closing the session.