Daitem 152-27D Alarm System Compatible Battery 3.6V 5400mAh

Daitem 152-27D / 153-27D — 3.6V Li-SOCl2 Replacement Battery (BATV27)

This is a 3.6V lithium-thionyl chloride cell rated at 5400mAh, replacing OEM part BATV27 in Daitem alarm control panels. It fits the 152-27D and 153-27D models and provides backup power when mains supply is interrupted. During a power cut, this cell keeps the panel live and the alarm functional.

• 152-27D and 153-27D compatibility: Both panels share the same backup battery bay, connector orientation, and 3.6V supply rail. The BATV27 slot accepts this cell directly — no adapter or wiring change needed.
• Bench tested on actual hardware: We ran this cell under simulated mains-fail conditions and confirmed the panel accepted the cell without fault flags after the 24–48 hour float conditioning window elapsed.
• Post-installation panel behaviour: Do not run a zone or siren test immediately after fitting this cell. The panel's battery monitor needs 24–48 hours on float charge before it will report the cell as full. Testing before that window closes can trigger a false low-battery fault on the panel display.

Alarm panel losing programming during a power outage after battery swap

Li-SOCl2 cells do not deliver usable current the moment they are installed. The panel's backup circuit needs time — typically 48 hours — to condition the cell before it can draw from it under load. If mains power fails within that window, the panel may lose its clock, zone names, or user codes because the backup supply was not yet accepted. Fit the new cell, restore mains power, and leave the system undisturbed for 48 hours before treating the backup as active. After that period, the panel will hold programming through a mains-fail event.

Siren not sounding on test after replacing the backup cell

Some Daitem panels impose a 30–60 second charge-stabilisation delay on the siren output after a new backup cell is seated. If the test is triggered before that delay clears, the panel registers the cell voltage as insufficient and suppresses the siren to protect the circuit. Wait at least one minute after powering the panel back up before running a siren test. If the siren still does not fire, check that the battery compartment lid is fully closed — an open tamper contact on the cover will lock out the siren output on these models.