Fanuc alarm DS0306: APC ALARM: BATTERY VOLTAGE 0
servo APC alarm (absolute pulse coder) · Fanuc 0i-D
What it means
The backup battery voltage for the absolute position detector has dropped below the level needed to retain pulse counts, or the pulsecoder was powered for the first time (e.g., after battery disconnection). Absolute position data is now unreliable and the stored counts may have been lost. Replace the battery with the CNC power ON so counts stay valid; if the alarm returns after a power cycle, suspect the battery unit or its cable.
Likely causes
- Battery fully discharged or disconnected
- Battery cable open or connector not seated
- First-time connection of pulsecoder power after storage
- Defective battery holder/unit
Triage note: On older Series 16/18-A controls the same condition appears as APC alarm 306. After battery-zero events, a reference return and possibly zero-point reset (parameter No. 1815) is required.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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A98L-0031-0012
battery · Common cause
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A02B-0200-K102
battery · Common cause
Need the part urgently?
Send us alarm DS0306 with your machine details — typical RFQ turnaround is 24–48h.