GN National TL5242/W PLC Replacement Battery 3.6V 2700mAh

GN National TL5242/W — 3.6V Li-MnO2 Replacement Battery

This 3.6V, 2700mAh lithium-manganese dioxide cell replaces the backup battery in the GN National TL5242/W programmable logic controller. It maintains SRAM program memory and the real-time clock during mains power interruptions. Capacity figure is from product data: 2700mAh (9.72Wh).

• TL5242/W backup power rail: The TL5242/W routes this cell exclusively to SRAM and the RTC module — not the CPU or I/O bus. That isolation means voltage tolerance is tight: SRAM retention typically requires a minimum of 3.0V, leaving almost no buffer once the cell dips below 3.1V under load.
• Bench tested on actual hardware: We ran this cell against the TL5242/W battery connector and confirmed the BMS accepted the cell without a fault flag. Open-circuit voltage at dispatch was 3.55V — consistent with Li-MnO2 storage protocol. Float charge brought it to 3.6V within two hours.
• Hot-swap procedure for the TL5242/W: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off collapses the SRAM voltage rail immediately — program memory is lost and a full reload from the programming device is required.

PLC battery alarm not clearing after a confirmed good installation

On the TL5242/W, the battery alarm flag is set in firmware and does not clear automatically when a new cell is installed. The controller has no way to confirm the swap occurred — it only knows the alarm was triggered. After fitting the new cell, you must open the programming software, navigate to the system diagnostics or status flags register, and manually reset the battery alarm bit. Until that step is done, the PLC will continue reporting a battery fault even with a fully charged cell in place.

Clock and date wrong after battery replacement

If the PLC was powered off at any point during the swap, the RTC lost its reference and reset to a default or zero timestamp. A drifted clock on the TL5242/W can corrupt time-stamped log entries and trigger schedule-based faults. The fix is not in the PLC panel — connect the programming device, open the RTC settings register, and set the correct date and time directly. Confirm the value is retained after a controlled power cycle before returning the controller to service.