2XER18505M DSC Siren Res Fire Compatible Battery 3.6V 16000mAh

DSC PG9901 Siren Res Fire / Burg Siren Series — 3.6V Li-SOCl2 Replacement Battery (2XER18505M)

This is a 3.6V Li-SOCl2 cell rated at 16000mAh, replacing part number 2XER18505M in DSC wireless siren and fire alarm components. It fits the PG9901, Siren Res Fire, and Burg Siren devices. Li-SOCl2 chemistry is standard for this category — it holds voltage flat under low-current standby loads and tolerates years of continuous use without active charging.

• PG9901 and Siren Res Fire platform: These devices share the 2XER18505M cell format because they operate on the same DSC PowerG wireless platform, drawing low standby current from a primary (non-rechargeable) Li-SOCl2 cell. No charging circuit is involved — the panel monitors cell voltage to flag depletion, not charge state.
• Bench tested on actual hardware: We ran this cell against the OEM voltage profile. Open-circuit voltage read 3.68V on delivery. Under a simulated 40µA standby draw — typical for PG9901 supervision cycles — the voltage held within spec throughout the test window.
• Post-swap panel reset procedure: After installing this cell, clear the low-battery fault from the panel keypad before running any zone test. Li-SOCl2 cells can show a brief passivation dip on the internal impedance — wait at least 30 minutes post-install before triggering a full siren test, or the panel may log a fault against the new cell.

Why the PG9901 reports low battery hours after a fresh cell is installed

Li-SOCl2 cells have a passivation layer that forms on the lithium anode during storage. When the panel first polls the new cell, internal impedance is temporarily elevated, and the voltage under load reads lower than the actual state of the cell. The panel's BMS interprets this dip as a low-battery condition and raises an alert. The passivation layer dissolves within 30–60 minutes of the cell being under load, after which the panel should clear the fault on its next supervision cycle — typically within 24 hours.

Siren not sounding during test cycle after battery swap

If the siren fails to trigger during a manual test run shortly after replacing the cell, the device is likely still in its charge-stabilisation window — even though Li-SOCl2 cells are non-rechargeable, the PowerG siren module delays full activation output until the supervision signal confirms stable cell voltage. Wait at least 30–60 minutes after install before running a test. If the siren still does not sound after that window, pull the device from the bracket and confirm the battery contacts are seated flush — the 2XER18505M must make firm contact on both terminals. Confirm open-circuit voltage reads above 3.5V before re-seating.