About this replacement
Bosch Rexroth MKE037 / MKE047 / MKE098 — 3.6V Li-SOCl2 Replacement Battery (R911277133)
This 3.6V lithium-thionyl chloride cell replaces the backup battery in Bosch Rexroth MKE037, MKE047, and MKE098 servo motors and their associated Rexroth drive controllers. It delivers 1200mAh (4.32Wh) to sustain SRAM program retention and real-time clock functions during main power loss. OEM part numbers R911277133 and R911281394 both cross to this cell.
- MKE037 / MKE047 / MKE098 platform fit: All three MKE series units share the same backup battery bay, connector pinout, and 3.6V SRAM retention rail. One cell covers the full platform — no adapter or rewiring needed.
- Bench tested on actual hardware: We ran this cell against the Rexroth BMS handshake and confirmed steady 3.6V delivery to the retention rail. The controller accepted the cell without a fault code on initial installation with the PLC powered and in RUN mode.
- Hot-swap procedure — MKE series controllers: Always replace this battery with the controller powered on and in RUN mode. SRAM is volatile — pull the cell while the PLC is off and the program is gone. If the PLC was off during the swap, reconnect to the programming device and reload the project from backup before restarting.
PLC losing program memory after battery swap on Rexroth MKE controllers
The MKE series holds its program in static RAM, not flash. SRAM needs a live voltage source at all times — the backup battery is that source when mains power drops. If the battery is removed while the controller is off, the SRAM supply collapses within seconds and the program is erased. This is not a fault in the new cell — it is the result of a cold swap. Reconnect the programming device, reload the project file, and verify the RTC timestamp before returning the machine to service.
Battery alarm not clearing after new cell is installed in Rexroth drive
The Rexroth IndraWorks diagnostic system latches a battery alarm flag independently of the cell's actual state. Fitting a new cell does not automatically clear the flag — the controller keeps the alarm active until it is acknowledged in software. Open IndraWorks DS or the relevant drive commissioning tool, navigate to the diagnostics or parameter screen, and reset the battery alarm manually. Confirm the cell voltage reads at or above 3.5V in the parameter list before clearing the flag.