Siemens alarm 2100: NCK battery alarm (backup battery voltage low)
SINUMERIK NCK hardware alarm (battery) · Siemens 840D/810D powerline
What it means
Voltage of the NCU backup battery (SRAM retention) below threshold; buffered NC/PLC data at risk on power loss.
Likely causes
- battery end of life (typical 3-5 years)
- battery holder contact corrosion
- NCU battery charging circuit fault (rare)
Triage note: Replace battery with NCU powered ON to retain SRAM contents; on 840D sl the corresponding alarm is 101000 (warning threshold reached). After any battery loss expect full reload + referencing.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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NCU backup battery (Siemens-approved lithium cell per NCU version)
NCU backup battery · Primary suspect
Need the part urgently?
Send us alarm 2100 with your machine details — typical RFQ turnaround is 24–48h.