Allen-Bradley 1756-BA2 PLC Control Battery for 1756 Controllers

Description

Product Overview

The 1756-BA2​ is a 3 V lithium primary battery manufactured by Allen-Bradley, a brand of Rockwell Automation, and serves as the dedicated backup-power source for the volatile memory and real-time clock of the Bulletin 1756 ControlLogix family of programmable logic controllers. Housed in a standard coin-cell form factor and occupying a dedicated battery slot on the controller module, the 1756-BA2​ maintains the controller’s user program, data tables, task schedules, and calendar information when the control chassis is without primary power. Without a healthy 1756-BA2​ in place, a loss of AC or DC supply to the chassis results in total loss of the application and a faulted controller on restoration — a condition that can turn a routine power outage into a lengthy restart and reconfiguration event.The chemistry and capacity of the 1756-BA2​ are deliberately chosen for the application. At approximately 1000 mAh and a nominal 3 V output, the cell provides the low, steady current required by CMOS memory and a crystal time base rather than the high surge current needed to start a motor or close a contactor. Under the typical load of a ControlLogix controller in standby, the 1756-BA2​ supports a service interval measured in years, and its self-discharge rate is low enough to give the cell a ten-year shelf life when stored at room temperature. This means a plant can stock the 1756-BA2​ as a shelf spare without worrying that the inventory itself has expired. The operating temperature range of –40 °C to +85 °C matches the storage and shipping envelope of industrial components, and the cell’s sealed construction prevents leakage that could damage the controller’s battery holder or the printed circuit beneath it. Because the 1756-BA2​ is a primary (non-rechargeable) lithium cell, it is intended to be replaced, not cycled, and the controller’s firmware reports battery status so that replacement can be scheduled during a planned maintenance window rather than discovered during an outage.

Technical Specifications

Main Features and Advantages

Years of backup from a single cell:​ The 1756-BA2​ is sized so that a single cell supports the memory and clock of a ControlLogix controller for a minimum of one year under load, with many installations seeing considerably longer life. This service interval is long enough that battery health becomes a scheduled maintenance item rather than a recurring emergency, and it allows plants to align battery replacement with annual shutdowns or turnarounds instead of reacting to a fault.A ten-year shelf life that makes stocking sensible:​ At approximately 1000 mAh and with lithium chemistry’s inherently low self-discharge, the 1756-BA2​ retains its capacity on the shelf for a decade at room temperature. Unlike consumables whose expiration must be tracked, the cell can be purchased in quantity, stored in a normal parts crib, and trusted when needed. For plants that operate multiple ControlLogix chassis, this turns battery management into a simple matter of keeping a box on hand rather than a just-in-time procurement exercise.Controller-reported health rather than guesswork:​ The 1756-BA2​ status is read by the controller firmware and exposed as a status bit, so a weakening cell shows up in the controller’s fault list and can be routed to the HMI, to an alarm, or to a maintenance work order long before the voltage falls far enough to threaten memory. This is materially better than a battery that fails silently: the 1756-BA2​ gives the maintenance team time to replace it during a planned window with the controller still running, avoiding the far worse scenario of discovering the failure during an unplanned power loss.A clean, leak-resistant physical design:​ The 1756-BA2​ is a sealed primary cell, so there is no electrolyte to leak onto the controller’s battery holder or the circuit board below. In the warm, sometimes dirty interior of an industrial control cabinet, this is a meaningful reliability advantage over older battery technologies. Because the cell is non-rechargeable, it cannot be overcharged or reverse-charged by the controller’s support circuitry, and the simple chemistry gives predictable end-of-life behavior rather than a sudden internal short.

Application Field

The 1756-BA2​ is used wherever a ControlLogix controller must survive a loss of primary power with its application and clock intact. In continuous process plants — refineries, chemical facilities, power generators, and water treatment works — the 1756-BA2​ protects the user program, recipe data, and historical trend buffers through utility outages, load-shedding events, and planned maintenance shutdowns. In these environments, a controller that loses its program does not merely inconvenience the operator; it can delay a safe restart by hours and require engineering resources to reload and reverify the application.In manufacturing, the 1756-BA2​ is equally important on packaging lines, assembly cells, and material-handling systems where the controller may be powered down for a weekend, a tool change, or a machine relocation. Without a healthy battery, the next startup begins with a faulted controller and a blank program, turning what should be a routine Monday morning into a recovery operation. Food and beverage, pharmaceutical, and consumer-goods OEMs routinely include a 1756-BA2​ replacement interval in their preventive maintenance schedules, treating the battery as a consumable with a known life rather than a fit-and-forget component.The 1756-BA2​ also sees service in remote and unmanned installations — pump stations, pipeline valve sites, and telecom or utility substations — where a technician may not visit for months at a time. In these locations, the controller’s ability to retain its program and its real-time clock through long power interruptions is not a convenience but a requirement for correct sequencing and for time-stamped event recording. Because the cell is reported by the controller firmware, even a remote site can have its battery health monitored centrally, allowing a spare to be dispatched before the next outage.