Allen Bradley 1766-L32xxx PLC Replacement Battery 6V 2900mAh

Allen Bradley MicroLogix 1400 / 1766-L32xxx — 6V Li-MnO2 Replacement Battery

This is a 6V, 2900mAh Li-MnO2 backup battery for the Allen Bradley 1766-L32xxx CompactLogix and MicroLogix 1400 series PLCs, as well as the BA 1764-LxP and MicroLogix 1500. It powers the onboard real-time clock module when main supply is removed, keeping date, time, and SRAM contents intact across power cycles.

• MicroLogix 1400 / 1766-L32xxx platform fit: These controllers share the same 6V backup rail, battery footprint, and BMS handshake protocol. A single cell format covers the full 1766-L32xxx variant range, including L32AWA, L32BWA, L32BXB, and related suffixes. The same applies across the MicroLogix 1500 and BA 1764-LxP where the clock module draws from an identical backup circuit.
• Bench tested on actual hardware: We ran this cell on a 1766-L32BWA under load cycling. The BMS held float charge at 6.2V with no fault codes triggered. SRAM retention stayed solid through a simulated 30-second main power dropout with the cell installed correctly.
• Live-swap requirement on MicroLogix: Always replace this battery with the PLC powered on and in RUN mode. The MicroLogix series has no supercapacitor buffer — removing the cell while the controller is off immediately collapses the SRAM voltage rail. Program memory is lost the moment the cell is disconnected with no main power present.

SRAM retention voltage threshold on the MicroLogix 1400

The MicroLogix 1400 SRAM array requires a minimum of approximately 3.0V at the backup rail to hold its contents. A depleted Li-MnO2 cell at end-of-life typically reads between 4.5V and 5.0V under no-load — still above the SRAM floor, but too low for reliable RTC oscillator operation. This means the clock can lose sync well before program memory is affected. Once the cell drops below roughly 5.2V, Allen Bradley recommends treating it as due for replacement regardless of whether a battery alarm has triggered yet.

Battery alarm still showing after a new cell is installed

The 1766-L32xxx does not auto-clear a battery low alarm after a cell swap — the flag is latched in the controller's status file. After installing the new cell, connect to the PLC via RSLogix 500 or Studio 5000, navigate to the controller properties or status file (S:2 word), and clear the battery fault bit manually. If the alarm persists after clearing, verify the new cell is seated fully in the connector and reading above 5.8V at the backup terminals before attempting a second clear.