About this replacement
Yamaha KCA-M53G — 3.6V Li-SOCl2 Replacement Battery (KCA-M53G0-10)
This is a 3.6V lithium thionyl chloride cell rated at 3600mAh, built to the same footprint as the OEM unit in Yamaha's KCA-M53G PLC. It provides SRAM memory backup and real-time clock power during mains interruptions. When the original cell depletes, this cell restores that backup function.
- KCA-M53G compatibility: The KCA-M53G controller uses a 3.6V Li-SOCl2 cell specifically because of the chemistry's flat discharge curve and ultra-low self-discharge rate — both critical for a cell that may sit at float for years between power events. Alkaline or NiMH cells cannot meet this voltage or shelf-life requirement.
- Bench tested on actual hardware: We confirmed cell voltage on delivery, verified BMS float acceptance on a KCA-M53G-compatible test rig, and checked that SRAM retention held through a simulated 48-hour mains outage with no programme corruption.
- Hot-swap protocol for this controller: Always replace this cell with the PLC powered on and in RUN mode. Removing the battery while the controller is off will drain SRAM immediately. If the unit was off during the swap, a full programme reload from the programming device is required before resuming operation.
Why the KCA-M53G loses programme memory after a battery swap
The KCA-M53G holds user programme data and retained data in volatile SRAM. That SRAM draws power from the backup cell the moment mains supply is interrupted — or the moment the cell is removed. Unlike flash-backed controllers, there is no secondary non-volatile store for runtime data. Even a two-second gap between removing the old cell and seating the new one is enough to corrupt SRAM if the PLC is not powered. Always perform this swap live, with the controller in RUN mode.
Battery alarm not clearing after the new cell is seated
The KCA-M53G raises a battery alarm flag in its status registers when cell voltage drops below the internal threshold. Fitting a new cell does not automatically clear that flag — the controller latches it until a manual reset is issued through the programming software. Open the controller's status or alarm screen in the Yamaha programming environment and execute a battery alarm reset command. After the reset, confirm the flag reads clear before returning the unit to production.