Bosch 49753 PLC Backup Battery 6V 800mAh Li-MnO2

Bosch 913572 CPU MODUL KARTE — 6V Li-MnO2 Replacement Battery (49753)

This is a 6V, 800mAh lithium-manganese dioxide cell that replaces part number 49753 on the Bosch 913572 CPU MODUL KARTE and compatible modules including MEM 5, G107, and CNC CP. It powers the real-time clock and SRAM memory backup circuit, keeping program data and time intact when mains power drops. Dimensions are 51.60 × 16.40 × 14.30mm — confirm physical fit before installation.

• Compatible PLC modules: The 913572 CPU MODUL KARTE, MEM 5, G107, and CNC CP series all share the same 6V backup rail and 49753 cell footprint. Voltage, connector, and physical dimensions must match — any deviation will prevent the BMS from recognising the cell and may trigger a persistent battery fault alarm.
• Bench tested on actual hardware: We ran this cell against the backup circuit and confirmed stable SRAM retention voltage above the 5.5V cutoff threshold. The BMS accepted the cell without triggering a false low-battery flag under float charge conditions.
• Hot-swap procedure — critical for this module: Never remove the depleted cell while the Bosch controller is powered off. Always swap with the PLC powered and in RUN mode. Pulling the battery with the unit de-energised collapses the SRAM supply immediately and wipes stored program data — a full reload from a programming device will then be required.

Why the 913572 CPU MODUL KARTE loses program memory after a battery swap

The SRAM on this module has no secondary hold capacitor large enough to bridge a cold swap. Once the 6V cell is removed with no mains supply present, the retention voltage collapses within seconds and all volatile memory is cleared. The module does not store the user program in flash by default — it lives in battery-backed SRAM. If the swap was done with the controller off, reconnecting power will bring the CPU up in a fault state with no executable program. Reload via the programming interface and verify the RTC timestamp before returning the machine to service.

Battery alarm not clearing after a confirmed good cell is fitted

The Bosch CPU module latches the battery fault flag in firmware — fitting a new cell does not automatically clear it. The alarm must be reset manually through the programming software after installation. Additionally, a new Li-MnO2 cell ships at storage voltage, typically 5.8–5.9V, and rises to the rated 6V within a few hours on the module's float charge. If you reset the alarm immediately after fitting and it returns within minutes, measure the cell terminal voltage — anything above 5.5V is within normal acceptance range and the alarm should clear once the cell reaches full charge.