About this replacement
Visonic PowerMaster 360 — 3.7V Li-Polymer Replacement Battery (103-305328)
This 3.7V 1300mAh lithium-polymer cell replaces the internal backup battery in the Visonic PowerMaster 360 and PowerMaster 360-pg2 wireless security control panels. It powers the panel's backup circuit, keeping wireless sensor communication and alarm alerts active during a mains failure. Capacity is 4.81Wh, matching the OEM specification exactly.
- PowerMaster 360 and 360-pg2 compatibility: Both panel variants use the same 3.7V Li-Polymer cell on the same backup power rail, with identical connector pinout and BMS handshake requirements. One cell fits both.
- Bench tested on actual hardware: We ran this cell through charge acceptance and discharge cycles on the PowerMaster platform. The panel BMS accepted the cell without fault codes, and float charge stabilised within the expected window.
- Post-installation charge window: Do not run a zone or diagnostic test immediately after fitting this cell. Allow 24 to 48 hours on float charge first. Running a test before the cell reaches full charge can trigger a false low-battery warning on the panel display.
Alarm panel showing low battery hours after installing a new cell
The PowerMaster 360 BMS monitors cell voltage against a threshold before clearing the low-battery flag. A new Li-Polymer cell ships at a storage charge — typically 3.6V to 3.75V — which sits below the panel's acceptance threshold. The panel will not clear the warning until the cell reaches approximately 3.9V to 4.1V under float charge. Leave the panel on mains power for 24 to 48 hours and the warning will clear on its own.
Panel loses zone programming during a mains outage after battery replacement
If the backup cell has not yet been accepted by the BMS, the panel cannot draw sufficient current from it during a mains outage. The result is a partial power-down that wipes volatile memory — sensor zones, user codes, and timing settings. This is not a fault with the cell itself. Condition the battery for 48 hours on mains before testing backup operation. After that window, a mains-off test should hold all programming.