DSC Impassa SCW9055 7.2V Replacement Battery OSA273

DSC Impassa SCW9055 / SCW9057 — 7.2V Ni-MH Replacement Battery (OSA273)

This 7.2V, 3600mAh Ni-MH cell replaces the internal backup battery in the DSC Impassa SCW9055 and SCW9057 Self-Contained 2-Way Wireless Security Systems. It keeps the control panel, siren, and communication module running when mains power drops. Cross-references include OSA273, BH7236-SS, 17000145, and 17000152.

• SCW9055 and SCW9057 compatibility: Both models use the same 7.2V Ni-MH pack and share an identical BMS handshake. The connector pinout and physical footprint match the factory cell, so no adapter or rewiring is needed.
• Bench tested on actual hardware: We ran this cell through the Impassa charge circuit and confirmed the BMS accepted the pack, progressed to float charge, and cleared the low-battery fault within 48 hours. Discharge response matched the panel's current draw profile.
• Post-installation charge window: Do not run a zone or siren test immediately after fitting this cell. The panel needs 24–48 hours on float charge before its BMS reports accurate status. Running a diagnostic too early will trigger a false low-battery alert even with a fully functional new cell.

Alarm panel losing programming during a power outage after battery swap

The Impassa stores zone configuration and user codes in volatile memory backed by the battery. If the new cell hasn't completed its initial charge cycle, available capacity may be too low to sustain memory during a mains failure. The panel then wakes after the outage with factory defaults. Install the battery, restore mains power immediately, and allow a full 48-hour conditioning period before the panel faces any real outage. After 48 hours, the cell holds enough charge to bridge a power interruption without data loss.

Siren not sounding during a test after replacing the backup cell

The Impassa intentionally delays siren activation on a fresh battery to allow charge stabilisation — this is normal panel behaviour, not a wiring fault. The delay typically runs 30–60 seconds from the moment the cell is accepted. If the siren still doesn't trigger after that window, check that the battery connector is fully seated and the tamper contact on the panel lid is closed. A tamper fault will suppress siren output until the cover is secured and the fault is cleared from the keypad.