Epic Systems EP5242W PLC Replacement Battery 3.6V 2700mAh

Epic Systems EP5242W / LTC16PFS8 — 3.6V Li-MnO2 Replacement Battery

This 3.6V, 2700mAh lithium manganese dioxide cell is the backup battery for the Epic Systems EP5242W and LTC16PFS8 programmable logic controllers. It powers the onboard real-time clock and SRAM memory retention during power loss or controller disconnection. Replace the original cell when the PLC logs a low-battery alarm or after 5–10 years of service.

• EP5242W and LTC16PFS8 compatibility: Both controllers share the same 3.6V backup rail, connector footprint, and BMS handshake requirements. One cell covers both platforms without modification.
• Bench tested on actual hardware: We ran this cell under float charge conditions and confirmed stable voltage delivery to the SRAM and RTC circuits. The cell held voltage above the 3.0V SRAM retention threshold throughout the test cycle.
• Hot-swap procedure — critical for this PLC: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is off cuts SRAM power immediately, wiping stored program memory. A cold swap means a full program reload from your programming device.

PLC losing program memory after battery swap

The EP5242W uses SRAM for program and data storage. SRAM is volatile — it requires continuous voltage to retain data. The backup battery is the only power source for that memory when mains power is removed. If the old cell is pulled while the PLC is off, SRAM drops below its retention threshold within seconds and all stored logic is lost. Always perform the swap live, with the controller powered and running.

Battery alarm not clearing after a confirmed good installation

Installing a fresh cell does not automatically reset the low-battery alarm on these controllers. The fault flag is latched in software and must be cleared manually through the programming interface. Connect your programming device, navigate to the fault or alarm register, and reset the flag once the new cell reads at or above 3.5V. If the alarm returns within 24 hours, check enclosure temperature — a warm cabinet accelerates self-discharge and can trigger the alarm threshold faster than expected.