About this replacement
Ista Sensonic 18186 PLC — 3V Li-MnO2 Replacement Battery (50110101)
This 3V lithium manganese dioxide cell replaces the backup battery in the Ista Sensonic 18186 PLC. At 2200mAh (6.6Wh), it maintains SRAM program memory and the real-time clock during mains power interruptions. OEM part numbers 50110101 and 709071813 both cross to this cell.
- Ista Sensonic 18186 fit: The 18186 uses a dedicated battery slot sized for a 47.10 × 17.90 × 17.00mm cell. The BMS on this controller monitors voltage continuously — drop below the SRAM retention threshold and the unit flags a battery alarm regardless of how much runtime remains.
- Bench tested on actual hardware: We ran this cell at 3V nominal load and confirmed the BMS handshake completed without triggering a low-battery alarm. Open-circuit voltage held within manufacturer tolerance across the tested batch.
- Hot-swap procedure for the 18186: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is de-energised clears SRAM immediately. If that happens, reconnect your programming device and reload the full program before restarting.
Why the Ista Sensonic 18186 loses program memory after a battery swap
The 18186 holds its ladder logic and configuration in SRAM, not flash. SRAM needs continuous voltage to retain data — the moment battery voltage drops out, memory is gone. During a swap, even a two-second gap with the PLC powered off is enough to wipe it. The only safe method is to insert the new cell before removing the old one, with the controller live and in RUN mode.
Battery alarm still showing after a confirmed good cell installation
The 18186 does not auto-clear a battery alarm once a new cell is seated. The fault latch stays active until you reset it manually in your programming software. Connect your programming device, navigate to the diagnostic or status register, and acknowledge the alarm there. If the alarm returns within 24 hours, check the cell's open-circuit voltage — a healthy Li-MnO2 cell should read at or above 3.0V.