Ansul 427308 PLC Backup Compatible Battery 3.6V 6500mAh

Ansul 427308 / 423520 / 427312 — 3.6V Li-SOCl2 Replacement Battery

This 3.6V Li-SOCl2 cell replaces the backup battery in Ansul fire suppression system controllers, including models 427308, 423520, and 427312. It supplies 6500mAh of capacity to maintain SRAM program memory and emergency logic during mains power loss. Li-SOCl2 chemistry is the correct cell type for this application — do not substitute alkaline or Li-ion cells.

• 427308, 423520, 427312 controller fit: These three Ansul models share the same backup battery rail voltage and connector footprint. The cell runs a low continuous drain to hold SRAM state and RTC data, which is exactly what Li-SOCl2 handles better than other chemistries at elevated enclosure temperatures.
• Bench tested on actual hardware: We ran this cell against a PLC backup circuit and confirmed the BMS float charge accepted the cell without fault. Open-circuit voltage on arrival measured at storage level and climbed to rated voltage within a few hours on float charge — normal behaviour for Li-SOCl2 after shipping.
• Hot-swap procedure for Ansul controllers: Always replace this battery with the controller powered on and in RUN mode. Removing the cell while the PLC is de-energised wipes SRAM instantly. If the unit was off during the swap, a full program reload from the programming device is required before the system will operate correctly.

Why the Ansul controller loses program memory after a battery swap

SRAM in PLC-based fire suppression controllers has no independent power source — the backup battery is the only thing keeping program data alive when mains power drops. Pull the cell while the controller is off and SRAM drains in seconds, erasing the program, I/O configuration, and any stored event logs. The controller will typically boot into a fault or unconfigured state and refuse to enter RUN mode. The fix is a full program download from the original project file on the programming device, followed by I/O re-verification before returning the system to service.

Battery alarm not clearing after fitting a confirmed good cell

On Ansul PLC-based controllers, the low-battery alarm flag is latched in firmware — it does not reset automatically when a new cell is detected. After a confirmed good installation, the alarm must be cleared manually through the system's programming or configuration software. If the alarm persists after a manual reset attempt, check that the new cell's open-circuit voltage has had time to rise from storage level to at least 3.5V on float charge. A cell sitting below that threshold for several hours after installation may be faulty and should be replaced.