Mitsubishi A6BAT Compatible Battery 3.6V 1700mAh Li-SOCl2

Mitsubishi A Series PLC — 3.6V Li-SOCl2 Replacement Battery (A6BAT)

This is a 3.6V 1700mAh lithium thionyl chloride cell that replaces the A6BAT in Mitsubishi A Series PLCs. It maintains SRAM program memory and real-time clock data when main power drops. Compatible models include A Series PLCs, A1FX CPU Robot Control PLC, A1FXCPU Robot Control PLC, A1S, and 28 additional variants in the A Series range.

• A Series CPU module compatibility: These CPUs share the same battery bay footprint, connector pinout, and 3.6V SRAM retention rail. The BMS handshake is passive — the cell supplies voltage directly to the memory backup circuit without any protocol exchange.
• Bench tested on actual hardware: We verified cell voltage at dispatch and confirmed SRAM retention hold-up across the A1S CPU module. The backup circuit drew steady microamp-level current with no anomalous drain during the test window.
• Hot-swap procedure for A Series CPUs: Always replace this cell with the PLC powered on and in RUN mode. Removing the battery while the controller is off clears SRAM instantly — the entire program is lost and must be reloaded from a programming device before the PLC will run again.

Why the A Series PLC loses program memory during a battery swap

The A Series CPU uses static RAM for program and parameter storage. SRAM needs continuous voltage to hold its contents — even a two-second gap is enough to wipe everything. Unlike flash-based CPUs, there is no secondary storage layer to recover from. When the battery is pulled with the PLC off, the SRAM supply collapses and the memory clears immediately.

Battery alarm not clearing after confirmed good installation

The A Series battery low alarm does not reset automatically when a new cell is fitted. The alarm flag is written to a specific status register in the CPU and must be cleared manually using GX Developer or GX Works via the PLC diagnostics menu. A new cell at storage voltage may also read slightly below 3.6V on first install — this rises to rated voltage within a few hours on float charge. Clear the alarm flag after voltage has stabilised, not immediately after swapping the cell.