ADT SCW9057G-433 Replacement Battery 7.2V 3600mAh

ADT SCW9057G-433 / Impassa — 7.2V Ni-MH Replacement Battery (OSA273)

This is a 7.2V 3600mAh Ni-MH replacement battery for the ADT SCW9057G-433 and Impassa wireless alarm systems. It fits the handheld remote keypad used to arm and disarm the alarm wirelessly. OEM part numbers OSA273, BH7236-SS, 17000145, and 17000152 all cross-reference to this cell.

• SCW9057G-433 and Impassa compatibility: Both platforms share the same 7.2V Ni-MH battery specification and connector format. The Impassa uses the same remote keypad architecture, so the BMS handshake and charge acceptance behaviour are identical across both devices.
• Bench tested on actual hardware: We cycled this cell through a full charge-discharge sequence on the SCW9057G-433 keypad. The BMS accepted charge normally, reported full capacity after a 24-hour float, and showed no voltage drop or fault codes during discharge testing.
• Post-installation float charge period: Do not run a zone or diagnostic test immediately after fitting this battery. Allow 24 to 48 hours on float charge first. The panel's BMS needs that window to accept the new cell — running a test before that point can trigger a false low-battery alert.

Alarm panel showing low battery hours after installing a new cell

Ni-MH cells don't report as fully charged the moment they're installed — the panel's BMS monitors voltage over time before it clears the low-battery flag. On the SCW9057G-433 and Impassa, that process typically takes 24 to 48 hours on trickle charge. If the panel is still showing the fault after 48 hours, check the terminal connections first. A voltage reading of 7.2V or above at the connector confirms the cell is good and the panel should clear the alert automatically.

Alarm losing programming during a mains power outage after battery swap

If the panel drops its zone programming or user codes during a power cut, the backup battery hadn't fully conditioned before the outage hit. A freshly installed Ni-MH cell holds a surface charge from shipping but hasn't yet built the capacity buffer the panel needs to retain memory under load. Let the system run on mains power for at least 48 hours after fitting the new battery before relying on it for backup. After a full conditioning cycle, the cell will sustain panel memory through a standard outage without data loss.