SV0306 APC Battery Voltage 0 (Data Lost) fault in Fanuc drive

SV0306 APC Battery Voltage 0 (Data Lost) fault in Fanuc drive

Description

SV0306 is the severe version of the battery alarm. While SV0307 represents "Low Battery" (Warning), SV0306 means "Dead Battery." The voltage on the memory backup circuit for the Absolute Pulse Coder dropped below the critical threshold (usually 2.5V) while the machine was powered off. Consequently, the position data in the encoder's RAM has been wiped out. The machine no longer knows where "Home" is. Even if you replace the battery now, the data is already gone.

Cause

• Neglect: Ignoring the SV0307 warning for weeks until the battery finally died.
• Cable Disconnect: Unplugging the encoder cable from the motor while the drive was powered off. The encoder relies on the drive's battery via the cable.
• Battery Corrosion: The battery contacts in the battery box are corroded, breaking the circuit even if the batteries are new.
• Short Circuit: A pinched feedback cable draining the battery to ground.

Solution

You must re-establish the zero point.

1. Replace Battery: Install fresh alkaline or lithium batteries (Fanuc standard 6V pack).
2. Clear Alarm: You often need to power cycle the machine to clear the 306 code; it will change to SV0300 (Request for Reference).
3. Mastering/Grid Shift:
   • If the machine has limit switches (Dogs), perform a manual Reference Return.
   • If "Dogless," you must perform the APZ (Absolute Position Zero) procedure using Parameter 1815. Jog the axis to the alignment marks, set 1815.4 (APZ) to 0, then 1, and restart.