About this replacement
ABB AC400 Systems — 12V Ni-MH Replacement Battery (3BSC760015R1)
This is a 12V 3600mAh Ni-MH backup battery for the ABB AC400 PLC system. It fits AC400 and AC400 Systems controllers. The battery holds SRAM program memory and keeps the real-time clock running during mains power loss.
- AC400 platform compatibility: ABB AC400 controllers route backup power through a single cell bay on a shared 12V rail. All AC400 variants using part number 3BSC760015R1 or SB522V1 draw from this same rail, so one cell covers the full platform without connector or BMS mismatch.
- Bench tested on actual hardware: We cycled this cell through float charge and simulated mains dropout. The BMS held SRAM retention voltage above the AC400 cutoff threshold and recovered to float charge without fault flags on restore.
- Hot-swap procedure on the AC400: Never remove this battery while the PLC is powered off. Always swap the cell with the controller in RUN mode and mains power present. Removing the cell while the PLC is off clears SRAM — the full program must then be reloaded from a programming device before the controller will run.
AC400 battery alarm not clearing after a confirmed good installation
The AC400 does not automatically clear a battery alarm once a new cell is fitted. The alarm latches in the controller's diagnostic register and stays active until it is manually acknowledged through the programming software. Connect via the programming tool, navigate to the system diagnostics or alarm log, and reset the battery fault flag. The alarm clears immediately — no controller restart needed.
New cell reading lower than 12V on the AC400 status display
Ni-MH cells ship at a reduced storage voltage — typically 10.5V to 11V — to slow self-discharge during transit. The AC400 float charger brings the cell up to full voltage within a few hours of installation. If the display still reads below 11V after 24 hours on a powered controller, check that the cell connector is fully seated and the controller is not in a low-power standby mode that suspends charging. A correctly installed cell should read at or above 12V within one charge cycle.