Allen-Bradley 1757-BEM Replacement for ProcessLogix Series

Product Overview

Allen-Bradley 1757-BEM Replacement for ProcessLogix Series: Smooth Transition & Legacy System Compatibility

The Allen-Bradley 1757-BEM Battery Extension Module is a critical backup power component within the Rockwell Automation ProcessLogix 1757 distributed control system (DCS) platform. As the 1757 series has reached end-of-life and spare parts availability continues to tighten, facilities running legacy ProcessLogix controllers face increasing pressure to source reliable replacement modules before unplanned downtime forces emergency shutdowns. TOPNLMS maintains verified stock of the 1757-BEM and ships globally from Xiamen, China, with full pre-shipment functional testing and a 12-month warranty on every unit.

The 1757-BEM is designed to extend battery backup duration for the ProcessLogix controller chassis, ensuring that volatile memory — including ladder logic programs, configuration data, and real-time process values — is retained during power interruptions. In aging DCS environments where the primary controller may be a 1757-PLXC1 or 1757-PLXC2 processor module, the battery extension module plays a non-negotiable role in system integrity. Replacing a failed or degraded 1757-BEM with a verified unit restores full backup autonomy without requiring any firmware changes, program re-downloads, or reconfiguration of the host controller.

For plants currently operating ProcessLogix systems alongside legacy I/O infrastructure — including 1757-SRM (System Redundancy Module) configurations or 1757-PLXIB I/O bus interfaces — the 1757-BEM slots directly into the existing chassis backplane without mechanical modification. The module draws power from the standard 1757-series power supply rail, and its connector pinout is fully backward-compatible with all known ProcessLogix chassis revisions. Engineers performing a like-for-like swap can complete the replacement during a scheduled maintenance window without altering field wiring, I/O mapping, or communication network topology.

Many facilities undertaking a broader migration from ProcessLogix to a modern PlantPAx or ControlLogix architecture choose to maintain the 1757 platform in parallel during the transition period. In these hybrid environments, the 1757-BEM ensures that the legacy DCS segment remains stable while new ControlLogix L7x or L8x controllers are commissioned on the same network. Communication continuity is maintained through existing ControlNet or EtherNet/IP backbones, and the battery module’s presence prevents data loss on the legacy side during any power cycling events associated with the new system installation.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful ProcessLogix battery module replacement rarely happens in isolation. In most retrofit and upgrade projects, the 1757-BEM is sourced alongside a broader set of components to ensure the entire control system remains operational through the transition. Facilities commonly procure the 1757-PLXC2 processor module as a hot-standby spare, ensuring that if the primary controller fails during the maintenance window, a tested replacement is immediately available. The 1757-SRM System Redundancy Module is another frequent companion purchase, particularly in high-availability process environments where controller switchover must occur without interrupting field I/O.

On the I/O side, plants migrating from older analog and digital I/O racks often source 1757-PLXIB I/O bus interface modules to maintain connectivity between the ProcessLogix controller and legacy field devices during the transition. Where communication infrastructure is being upgraded in parallel, 1757-series ControlNet communication modules are retained to preserve existing network topology while new EtherNet/IP segments are brought online. For facilities that are simultaneously upgrading their HMI layer, PanelView Plus 7 terminals are commonly integrated as the new operator interface, communicating with the legacy ProcessLogix system via ControlNet until full migration to PlantPAx is complete.

Power infrastructure is another area requiring attention during a 1757-BEM replacement project. The 1757-series redundant power supply modules should be inspected and, if approaching end-of-life, replaced concurrently to avoid a secondary failure shortly after the battery module swap. Signal isolation is also a consideration in older installations: DIN-rail mounted signal isolators are frequently added to protect the new module from ground loops or noise introduced by aging field cabling. Finally, for commissioning and diagnostics, a 1784-U2CN ControlNet USB interface cable or equivalent programming cable is essential for connecting a laptop running RSLogix or Studio 5000 to the ProcessLogix chassis for post-replacement verification and program integrity checks.

Retrofit Guidance FAQ

Q: Do I need to re-download the PLC program after replacing the 1757-BEM?
A: No. The 1757-BEM is a battery extension module, not a processor or memory module. Replacing it does not affect the program stored in the 1757-PLXC processor. However, it is best practice to perform a program backup via RSLogix before any hardware swap.

Q: Is there any wiring change required during installation?
A: No field wiring changes are required. The 1757-BEM connects via the ProcessLogix chassis backplane. Simply power down the chassis per your site safety procedure, remove the failed module, insert the replacement, and restore power.

Q: Will the replacement module work with both 1757-PLXC1 and 1757-PLXC2 processors?
A: Yes. The 1757-BEM is compatible with all ProcessLogix processor variants that support the battery extension slot. No firmware or configuration changes are needed on the processor side.

Q: Can I install the 1757-BEM while the system is running (hot-swap)?
A: Hot-swap capability depends on your specific chassis revision and site safety policy. In most ProcessLogix installations, a controlled power-down is recommended for battery module replacement to avoid transient voltage events. Consult your system documentation and site procedures before attempting a live swap.

Q: What communication protocols does the ProcessLogix 1757 platform support?
A: The ProcessLogix 1757 platform primarily uses ControlNet for controller-to-I/O and controller-to-controller communication, with EtherNet/IP available for HMI and supervisory connectivity. The 1757-BEM itself does not participate in network communication — it is a power backup component only.

Q: How do I verify the replacement module is functioning correctly after installation?
A: After installation, use RSLogix or Studio 5000 to connect to the 1757-PLXC processor and check the module status in the I/O tree. The battery extension module should report a healthy status with no fault codes. LED indicators on the module face should also confirm normal operation per the 1757-BEM installation manual.

Warranty Assurance

Every 1757-BEM unit shipped by TOPNLMS is covered by a 12-month warranty from the date of delivery. Prior to shipment, each module undergoes a functional pre-shipment inspection to verify physical integrity, connector condition, and basic electrical continuity. Units that do not pass inspection are not shipped.

In the event of a warranty claim, TOPNLMS provides a replacement unit or full refund depending on the nature of the defect and the customer’s preference. Our after-sales response target is within 24 business hours of a warranty claim submission. Customers are not required to return the defective unit before a replacement is dispatched in most cases — we prioritize minimizing your downtime over administrative process.

For procurement teams requiring documentation, TOPNLMS can provide a packing list, commercial invoice, and certificate of conformance upon request. Bulk orders for maintenance spares programs are welcome, and volume pricing is available for orders of 3 or more units. Lead time for in-stock units is typically 3 business days from order confirmation to shipment from Xiamen.

To place an order or request a quotation, contact our technical sales team directly:

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