Fanuc alarm BAT: MEMORY BACKUP BATTERY LOW (flashing BAT warning)
battery/memory alarm · Fanuc 0i-D
What it means
When the lithium battery backing the CNC's SRAM (parameters, part programs, offsets, PMC ladder) falls below the detection threshold, 'BAT' flashes at the bottom of the screen and a battery alarm signal is output to the PMC. Data is still being retained, but Fanuc specifies replacement within about one week; if the battery dies completely with the control off, all SRAM contents are lost and the machine must be fully reloaded and re-referenced.
Likely causes
- Lithium cell past its ~1-3 year service life
- Battery not connected after board service
- Battery holder/cable contact corrosion causing low measured voltage
Triage note: Replace with the control POWERED ON so SRAM stays backed by the internal supply; note the exact PN printed on your battery before ordering - it varies by unit generation. APC/pulse-coder battery alarms are listed separately under servo/APC alarms.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
- Request a quote →
A02B-0200-K102 (3V lithium, CR17450SE-R type)
battery · Common cause
- Request a quote →
A98L-0031-0012 (equivalent 3V lithium pack)
battery · Common cause
- Request a quote →
A02B-0338-K106 (battery for later 0i-D/0i-F class units)
battery · Check if others ruled out
Need the part urgently?
Send us alarm BAT with your machine details — typical RFQ turnaround is 24–48h.