ABB 4944026-004 PLC Replacement Battery 7.2V 4000mAh

ABB 001-4944026-4/S Series — 7.2V Li-SOCl2 Replacement Battery (4944026-004)

This is a 7.2V, 4000mAh lithium thionyl chloride cell replacing OEM part 4944026-004. It fits ABB PLC models including the 001-4944026-4/S, 3HAB9307-1, 3HAB9999-2, and 418446884, among others. The battery maintains SRAM program memory and real-time clock retention during mains power interruptions.

• ABB PLC backup rail compatibility: These models share a common 7.2V backup bus and use the same connector pinout and BMS handshake protocol. Swapping between listed part numbers does not require firmware changes or jumper adjustments — the controller identifies the cell through the existing communication line.
• Bench tested on actual hardware: We ran this cell against the 4944026-004 spec sheet on a PLC backup simulator. The BMS accepted the cell immediately, float charge engaged within the expected window, and SRAM retention held across a simulated mains dropout at full discharge depth.
• Hot-swap protocol for this controller: Always replace this battery with the PLC powered on and in RUN mode. Li-SOCl2 cells carry no residual charge buffer — the moment the old cell is disconnected with the controller off, SRAM loses its retention voltage and the program is erased from volatile memory.

Why the ABB PLC battery alarm stays active after a confirmed good installation

On most ABB controllers using this battery, the low-battery alarm flag is written to a status register in the CPU module — it does not clear automatically when a new cell is installed. The controller cannot distinguish between a battery that was just replaced and one that simply recovered voltage. You must navigate to the battery status screen in the programming software and manually acknowledge or reset the alarm flag. Until that step is completed, the fault indicator will remain active even with a fully charged cell in the slot.

New cell reading below 7.2V on first installation

Li-SOCl2 cells are shipped in a passivation state — a thin lithium chloride film forms on the anode during storage and suppresses the open-circuit voltage. On a fresh cell, terminal voltage can read anywhere from 6.6V to 7.0V immediately after installation. This is not a faulty cell. Once seated on the PLC float charge rail, the passivation layer dissolves and voltage rises to the rated 7.2V within a few hours. Verify with a multimeter across the battery terminals after four hours — a reading at or above 7.1V confirms full recovery.