Visonic MC-S710 Replacement Battery 3.6V 14500mAh

Visonic MC-S710 / MC-S720 Series — 3.6V Li-SOCl2 Replacement Battery (0-9912-K)

This is a 3.6V lithium-thionyl chloride cell rated at 14,500mAh (52.2Wh), cross-referenced to OEM part 0-9912-K. It fits the Visonic MC-S710, MC-S720, MCS-730, and MCS-710 wireless alarm control panels. The Li-SOCl2 chemistry suits standby applications where the cell sits at float for months and must deliver full voltage on demand.

• MC-S710 / MC-S720 / MCS-730 platform fit: These panels share the same battery bay geometry, 3.6V supply rail, and supervisory circuit. All accept the ER34615M form factor with the same connector footprint, so the same cell covers the whole range without modification.
• Bench tested on actual hardware: We ran this cell against a load profile matching the panel's wireless transmission bursts and supervisory polling. The BMS accepted the cell without fault codes, and the supervisory voltage held above the low-battery threshold throughout the test cycle.
• Post-installation float period: Do not run a full zone diagnostic or siren test immediately after fitting this cell. Li-SOCl2 cells develop a passivation layer during storage; allow 24–48 hours on the panel's float charge before running any diagnostic test, or the panel may log a false low-battery event.

Alarm panel showing low battery hours after installing new cell

Li-SOCl2 cells build a lithium chloride passivation layer on the anode during storage. This layer raises internal resistance temporarily and causes the cell's terminal voltage to read low under the panel's load test. The panel's supervisory circuit samples voltage under a brief load pulse — if the cell hasn't had time to de-passivate, that pulse drops terminal voltage below the alarm threshold. Leave the panel powered on for 24–48 hours after fitting the new cell; the passivation clears and terminal voltage stabilises above 3.5V, clearing the fault.

Alarm losing saved programming during a mains outage with new battery fitted

If the panel loses its zone configuration or user codes during a mains failure, the backup cell is not yet supplying the panel's memory rail. A freshly installed Li-SOCl2 cell requires the panel's conditioning circuit to accept it — this handshake can take up to 48 hours from first installation. Until that window completes, a mains dropout will drop the memory-supply rail below the 2.8V threshold the panel needs to retain SRAM. Keep mains power on for at least 48 hours after fitting before treating the backup function as active.