Rockwell Automation 1757-BEM ProcessLogix Battery Extension Module Installation Instructions - Manual (Page 6)

6 ProcessLogix Battery Extension Module
Publication 1757-IN093B-EN-P - April 2004
1757-BEM Module Features
1757-BEM Functionality
The main function of the 1757-BEM (Battery Extension Module) is to provide battery
backup power for volatile memory IC's contained within a module, such as the 1757-PLX52.
The battery backup is useful for maintaining information (such as configuration databases)
during temporary power outages and weekend shutdowns.
The 1757-BEM is a separate, single-wide module that plugs into the ProcessLogix Controller
chassis. It incorporates the standard ICP plastic module cover and front door. Connection to
the backplane is via the standard ICP connector. The Battery Extension Module ships with
one battery un-installed.
Three (3) series-connected, sub-C size, nickel-cadmium cells makeup the battery pack. The
sourcing capacity is rated at 200mAh. The BEM provides 5 milliamps of DC current at 3.6
volts for a period of 240 hours on a full charge. This rating includes - in addition to actual
memory power - any current drawn by the support electronics.
Self Test Circuitry
The self-test circuitry on the BEM does the following:
• periodically tests for battery pack presence
• periodically tests the battery pack under load
These tests are performed only when primary Controller power is present.
Local indication of the state (health) of the battery system is provided via an indicator on the
front cover along with the capability for external/remote alarming in the event of battery
deterioration or failure.