About this replacement
Honeywell Home PROA7 Series — 3.7V Li-ion Replacement Battery (PROA7BAT2)
This 3.7V 5200mAh Li-ion cell replaces the OEM PROA7BAT2 backup battery in the Honeywell Home PROA7 alarm panel. It fits the PROA7, PROA7PLUS, Resideo PROA7C, and Resideo PROA7PLUSC control panels. When mains power drops, this cell keeps the panel armed, sensors active, and communications live.
- PROA7 and PROA7PLUS panel family: These four models share the same 3.7V single-cell architecture, identical connector pinout, and the same BMS handshake protocol — one battery covers all four without modification.
- Bench tested on actual hardware: We cycled this cell through charge and load on the PROA7 platform. The panel BMS accepted the cell, completed the charge handshake, and held float voltage without triggering a fault code.
- Post-install float charge period: Do not run a zone or siren diagnostic test immediately after swapping this cell. The panel needs 24–48 hours on mains power to bring the new cell to full float charge — testing before that window closes will cause the panel to report a low battery condition even though the cell is functional.
Alarm panel showing low battery hours after installing new cell
The PROA7 panel measures battery state continuously and flags low voltage before the cell reaches full charge. A brand-new Li-ion cell ships at approximately 30–50% state of charge — well below the panel's acceptance threshold. The panel needs 24–48 hours connected to mains power to complete the float charge cycle before the low battery warning clears. If the alert persists beyond 48 hours, check that the connector is fully seated and that mains power has not been interrupted during charging.
Panel loses all programming during a mains outage after battery swap
If the panel drops its zone configuration or user codes during a power cut, the backup battery was not yet accepted by the BMS at the time of the outage. The panel will not draw backup current from a cell it has not finished conditioning — this is a deliberate protection in the PROA7 firmware, not a fault with the battery. Allow at least 48 hours of uninterrupted mains power after installation before testing backup operation. After that window, trigger a controlled mains-off test and confirm the panel holds programming at 3.6V or above on the battery terminals.