SV0308 APC Alarm: Battery Low 2 (External) fault in Fanuc drive

SV0308 APC Alarm: Battery Low 2 (External) fault in Fanuc drive

Description

SV0308 is the counterpart to SV0307. While SV0307 usually refers to the battery plugged directly into the drive (CX5X), SV0308 often refers to the battery voltage of a "Separate Detector" (Scale) or an external battery box that feeds multiple encoders. This is common on large gantry machines where a central D-cell battery pack powers 4-6 motors. It is a pre-warning; position data is still safe.

Cause

• Dead Battery Box: The large alkaline D-cells in the external black Fanuc battery case are dead.
• Cable Break: The cable running from the battery box to the servo amplifier has a broken wire.
• Connector Corrosion: The battery box terminals are corroded (leaking batteries).

Solution

Warning: Keep power ON while changing.

1. Locate Box: Find the black battery box (often mounted on the floor of the electrical cabinet).
2. Check Voltage: Measure the voltage at the plug. It should be 6VDC.
3. Replace Cells: Replace the 4 D-cell batteries. Ensure polarity is correct.
4. Reset: Power cycle the machine to clear the alarm.