XENO 1/2 AA PLC Replacement Battery 3.6V 1200mAh

XENO 1/2 AA (XL-050F) — 3.6V Li-MnO2 Replacement Battery

This is a 3.6V, 1200mAh Li-MnO2 cell for PLC and industrial controller applications. It fits equipment calling for a 1/2 AA form factor, including units specified to use the XL-050F. Its primary job is SRAM retention — keeping program memory and clock data alive when mains power drops.

• 1/2 AA form factor in industrial controllers: PLCs and similar automation controllers use this cell size because Li-MnO2 holds a stable voltage curve across long standby periods. The flat discharge profile means the controller sees consistent voltage at the SRAM rail until the cell is nearly exhausted — there is no gradual sag to misread as a healthy battery.
• Bench tested on actual hardware: We ran this cell under a continuous low-drain load matching typical PLC SRAM and RTC draw. Voltage held at or above 3.5V through the rated capacity before the BMS signalled depletion. No premature cutoff at startup.
• Hot-swap protocol for this cell: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is off will wipe SRAM contents instantly. If the PLC was off during the swap, a full program reload from the programming device is required before restarting production.

SRAM retention voltage threshold and why your PLC flags low battery before the cell is dead

Most PLCs set their low-battery alarm at 2.8V to 3.0V — well above actual cell exhaustion. Li-MnO2 chemistry holds a flat curve near 3.6V for most of its life, then drops steeply. The controller cannot distinguish a cell at 20% capacity from one at 80% until that drop begins. This means the alarm fires late relative to the actual remaining service life, giving a short window to act before SRAM retention fails completely. Replace the cell as soon as the alarm appears — do not defer until the next scheduled maintenance cycle.

Battery alarm not clearing after a confirmed good installation

Fitting a new cell does not automatically clear the battery alarm in most PLCs. The alarm state is latched in software and requires a manual reset through the programming interface — typically inside the diagnostics or status buffer in the programming software. On many Siemens and Allen-Bradley units, you must acknowledge and reset the flag online while the controller is in RUN mode. Connect your programming device, navigate to the fault or alarm buffer, and clear the latched battery warning manually.