Dorma Protector 198027 3.6V Lithium Door Lock Replacement Battery

Dorma Protector Locking Cylinder — 3.6V Li-SOCl2 Replacement Battery (198027)

This 3.6V, 1200mAh lithium-thionyl chloride cell replaces part number 198027 in the Dorma Protector locking cylinder (model 298384). It powers the electronic access control mechanism inside the cylinder — the logic board, motor driver, and credential reader all draw from this single cell. Li-SOCl2 chemistry suits this application because it holds voltage flat across years of low-current standby draw.

• Protector cylinder fit (298384): The 198027 cell is sized specifically for the Protector cylinder housing — 25.70 × 16.00 × 14.50mm. The BMS in this cylinder monitors cell voltage directly; fitting a cell outside this voltage class or footprint will trigger a fault state and lock the mechanism.
• Bench tested on actual hardware: We cycled this cell through the Protector cylinder's wake-up sequence and credential validation loop. The BMS accepted the cell without fault codes, and the motor engaged cleanly on the first unlock command.
• Post-swap access verification: After fitting the new cell, run through every active credential — keypad code, card, and any app-based unlock — before closing the door. The Protector cylinder executes a firmware handshake after power interruption; some access methods stay locked out until that sequence completes.

Why the Protector cylinder ignores credentials immediately after a battery swap

When power is interrupted — even briefly during a battery change — the Protector cylinder's control board resets its internal state. The firmware runs a re-initialisation sequence before it will accept access commands again. If you try a card or code before that sequence finishes, the cylinder will not respond, and it can look like the new battery is faulty. Give the cylinder 15–20 seconds after inserting the cell before testing any credential. If it still does not respond, remove the cell, wait 10 seconds, and reinsert — this forces a clean boot cycle.

Low-battery alert triggering immediately after fitting a new cell

The Protector cylinder reads cell voltage on first boot and flags anything below its acceptance threshold. Li-SOCl2 cells that have been stored for extended periods can show a temporarily suppressed open-circuit voltage due to passivation — a thin lithium chloride layer that forms on the anode at rest. This causes the cylinder to read the cell as low or borderline even when it is genuinely full. Connect the cell briefly — one unlock cycle — to break down the passivation layer. The voltage should recover above 3.5V and clear the alert.