DEM K32RF Alarm System Replacement Battery 3.7V 1200mAh

DEM K32RF / PAR-120 — 3.7V Li-ion Replacement Battery

This 3.7V 1200mAh Li-ion cell replaces the internal backup battery in the DEM K32RF and PAR-120 wireless alarm control panels and associated security sensors. It measures 53.00 × 33.90 × 5.70mm — confirm these dimensions against your existing cell before ordering. Capacity is 4.44Wh as rated.

• K32RF and PAR-120 compatibility: Both panels share the same battery bay geometry, charge circuit voltage, and BMS handshake protocol. One cell covers either unit without modification.
• Bench tested on actual hardware: We cycled this cell through the K32RF charge circuit and monitored BMS acceptance. The panel registers full charge after a 24–48 hour float period — not immediately on power-up.
• Post-installation hold-off: Do not run a zone or siren diagnostic test immediately after fitting this cell. Allow 24–48 hours on float charge first. Running a test too early causes the panel to flag a low battery fault before the cell has reached its working voltage threshold.

Alarm panel showing low battery hours after installing new cell

The K32RF and PAR-120 both use a charge supervision circuit that samples cell voltage at regular intervals. A freshly installed cell typically sits at 3.5–3.6V out of packaging — below the panel's "healthy" threshold of around 3.7V. The panel will continue to report low battery until the onboard charger brings the cell to full float. This is expected behaviour and clears on its own after 24–48 hours on mains power.

Alarm losing saved programming during a power outage after battery swap

If the panel loses zone programming or user codes when mains power drops, the backup cell has not yet been accepted by the charge controller — the BMS is not yet supplying hold-up current. This happens when the panel is tested or power-cycled before the 48-hour conditioning window completes. Restore mains power, leave the panel undisturbed for 48 hours, then confirm cell voltage reads at least 3.7V before cutting mains again to test backup hold.