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Siemens SINUMERIK Controller
Power Supply · Intermediate · 10-20 minutes
Siemens Alarm 2100 - Battery Voltage Warning
SINUMERIK alarm 2100 fires when the NCK backup battery voltage drops below the warning threshold of approximately 2.7-2.9V. The battery monitoring circuit in the NCU continuously checks voltage levels and triggers this alarm to provide advance warning before complete battery failure.
2100
Siemens Alarm 2100 - Battery Voltage Warning
Block Not Executable
SINUMERIK 840D alarm 2100 indicates the NCK backup battery voltage has dropped to the warning threshold (approximately 2.7 to 2.9V). The battery is still functional but must be replaced within 6 weeks. This battery maintains SRAM data including tool offsets, workpiece data, and machine parameters during power-off. Machine operation continues normally at this stage. If the battery fails before replacement, all stored data will be lost and the control requires full re-initialization.
Root Cause Summary
SINUMERIK alarm 2100 fires when the NCK backup battery voltage drops below the warning threshold of approximately 2.7-2.9V. The battery monitoring circuit in the NCU continuously checks voltage levels and triggers this alarm to provide advance warning before complete battery failure.
Safety
- Program stopped
- ⚠️ PROGRAM EXECUTION STOPPED - Machine will not proceed until error is resolved
- Before troubleshooting, ensure the machine is in a safe state. Stop the program and power down the machine if necessary.
- Be aware of potential pinch points and moving parts when working around the machine.
- Disconnect power to the machine before performing any electrical troubleshooting. Lockout/Tagout procedures should be followed.
- Never bypass safety interlocks or guards.
- Consult the machine's safety manual for specific safety precautions.
Causes and Fixes
- 1
Check Battery Voltage
Navigate to HMI → Diagnostics → Hardware → NCU → Battery Status to verify current voltage reading and installation date.
Document the exact voltage reading - values below 2.8V indicate imminent replacement needed.
- 2
Verify Battery Age
Check machine documentation or battery label for installation date. Batteries older than 4 years should be replaced regardless of voltage.
Never remove the battery while the system is powered off - this will cause immediate data loss.
- 3
Order Replacement Battery
Order Siemens part number 6FC5247-0AA18-0AA0 (3V lithium) or system-specific equivalent from NCU documentation.
Keep a spare battery in stock - the 6-week warning window can pass quickly in production environments.
- 4
Schedule Hot-Swap Replacement
Replace battery during powered-on condition to maintain SRAM data integrity. Access battery compartment on NCU front panel.
Ensure system remains powered during battery replacement to prevent data loss.
Call a technician if:
- ·Alarm persists after battery replacement
- ·Multiple hardware alarms present
- ·Data loss has already occurred
Prevention
- Replace batteries every 3-4 years proactively
- Monitor battery voltage monthly via diagnostics
- Maintain proper NCU operating temperature
- Keep spare batteries in controlled storage
Common Mistakes
- Replacing battery with power off causing data loss
- Using non-Siemens compatible batteries
- Ignoring the 6-week replacement window
- Not backing up machine data before battery replacement
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Always verify with your machine manual or a certified technician before performing service procedures.