Absolute Pulse Coder Battery is Low
Fanuc · Series 20 CNC
What does 306 mean?
These alarms indicate that the backup battery for the absolute pulse coder, which maintains position data when the machine power is off, is running low. If not replaced, this will result in loss of absolute position data and require axis homing after every power cycle.
Common Causes
- Depleted battery for the absolute pulse coder.
- Loose or faulty battery connection.
- Issue with the battery charging circuit (if applicable, though typically for non-absolute encoders).
- Prolonged power-off periods draining the battery.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Locate and replace the absolute pulse coder battery (typically located on the servo amplifier or directly on the pulse coder) while the machine power is ON to prevent data loss.
- 2
Verify the battery voltage with a multimeter before and after replacement to ensure it's within specifications (e.g., 3.6VDC).
- 3
Ensure proper connection of the new battery.
- 4
Check relevant diagnostic screens to confirm the alarm clears after battery replacement.
- 5
If the alarm persists, inspect the battery holder and wiring for damage or corrosion.