Caliber 486 PLC Backup Battery 3.6V 2700mAh Li-MnO2

Caliber 486 / 486DX PLC — 3.6V Li-MnO2 Replacement Battery

This 3.6V, 2700mAh lithium manganese dioxide cell replaces the backup battery in Caliber 486 and 486DX programmable logic controllers. It maintains SRAM program memory and real-time clock data during mains power interruptions. When the original cell depletes, the controller loses configuration data on the next power cycle.

• 486 and 486DX compatibility: Both models use the same battery socket, voltage rail, and SRAM retention circuit. The 3.6V nominal matches the controller's memory-hold threshold, and the cell dimensions — 60.55 × 18.50 × 18.35mm — seat correctly in the factory holder without modification.
• Bench tested on actual hardware: We confirmed the cell holds the SRAM retention rail above 3.0V under micro-amp standby draw. The BMS on these controllers does not actively charge the backup cell — it floats, so voltage stability at rest is what matters, and this cell held steady.
• Hot-swap is mandatory on the 486: Always replace this battery with the PLC powered on and in RUN mode. Removing the depleted cell while the controller is off will wipe SRAM immediately. If the swap happens during a powered-off state, a full program reload from the programming terminal is required before restarting.

PLC losing program memory after battery swap on the 486

The 486 holds its ladder logic and configuration in volatile SRAM. That memory depends entirely on continuous voltage from the backup cell — there is no secondary hold circuit. If the cell is removed while the controller is off, even for a few seconds, SRAM loses power and the program is gone. The controller will boot into a fault or blank state on next power-up. Reconnect the programming terminal, reload the last saved project, and verify the I/O configuration before returning the machine to service.

Battery alarm not clearing after fitting a new cell

The 486 does not auto-clear a battery fault once a fresh cell is installed. The alarm flag is set in software and stays set until manually reset through the programming interface. Connect to the controller, navigate to the diagnostics or status register, and clear the battery fault bit explicitly. After clearing, confirm the cell voltage reads above 3.4V in the status display — that confirms the new cell is seated and the circuit is live.