Fanuc Batteries: Reliable Backup Power for Fanuc CNCs and Robots

Fanuc batteries maintain volatile memory and absolute encoder positions when a machine is powered down. Replacing them on schedule prevents parameter loss, re-mastering, and production delays.

What They Do

• Preserve CNC parameters, offsets, part programs, and robot mastering data during power-off.
• Provide backup to controls, servo amplifiers, and robot absolute encoders.
• Reduce the risk of reloading configurations and re-teaching positions after outages.

Battery Types and Typical Uses

Type	Where Used	Chemistry/Voltage	Typical Replacement Interval
Memory backup pack	CNC controllers and some servo amps	Primary lithium, commonly 3 V or 6 V packs	12–24 months in service (check manual/alarms)
Absolute encoder pack	Robots and machines with absolute pulse coders	Primary lithium, commonly 3 V or 6 V packs	Every 12 months or at first low-battery alarm
Rechargeable pack (NiMH)	Specific legacy or specialty systems	NiMH, system-charged	As specified by the system; monitor health more frequently

How to Choose the Right Fanuc Battery

• Match the controller/robot series: Check the nameplate and maintenance manual for the exact battery specification (controller series, servo amp type, and robot model can differ).
• Connector and pack configuration: Use the correct keyed connector and cell count (e.g., 2-cell, 4-cell). Do not modify connectors.
• Chemistry and voltage: Use like-for-like replacement (primary lithium vs NiMH, 3 V vs 6 V). Never substitute rechargeable for primary lithium unless the manual specifically allows it.
• Environment: Choose packs rated for plant conditions (temperature range, vibration). Store spares at 41–77°F (5–25°C), dry and dark.
• Fresh stock: Prefer recent date codes and sealed packaging. Rotate inventory first-in, first-out (FIFO).

Replacement Timing and Runtime Expectations

• Planned interval: Many facilities replace memory and encoder batteries every 12 months; some CNC memory packs can extend to 24 months if the manual allows. Always follow system alarms.
• After a low-battery alarm: Replace as soon as possible with main power ON. Do not postpone; some systems may retain data for only days to a few weeks once the alarm appears, and this is not guaranteed.
• Shelf life: Primary lithium packs typically offer 5–10 years shelf life if stored properly; install within the manufacturer’s recommended window.

Safe Replacement Procedure

Always consult your specific Fanuc maintenance manual. Most memory and encoder battery swaps should be done with the machine powered ON to avoid data loss.

1. Verify the exact part specification for your controller/robot and prepare the replacement pack.
2. Back up parameters/programs if possible (memory card, Ethernet, or maintenance software).
3. Ensure main power is ON and the machine is in a safe state. For robots, use the designated battery replacement mode if available.
4. Locate the battery compartment (controller cabinet, servo amp, or robot base/arm) and note connector orientation.
5. Unplug the old pack and promptly connect the new one. Avoid leaving the connector open for more than a few seconds.
6. Confirm alarms clear. Power-cycle only if the manual instructs. Record the date and update maintenance logs.
7. Dispose/recycle the old battery per local regulations (do not incinerate or disassemble).

Estimated time: 5–15 minutes per machine/axis, assuming easy access.

Good Practices That Prevent Downtime

• Replace batteries during scheduled PM and label the cabinet with the installation date.
• Keep two spare packs per critical machine; rotate stock annually.
• Never mix old and new cells or brands within a pack.
• Inspect contacts for corrosion or leakage; replace affected harnesses if needed.
• Back up CNC data and robot mastering before maintenance.

Avoid These Common Pitfalls

• Swapping with power OFF on systems that require power ON (causes memory loss and re-mastering).
• Using look-alike packs with incorrect voltage/connector.
• Substituting rechargeable cells where primary lithium is specified.
• Ignoring a battery alarm until the next outage.

Troubleshooting

• Low battery alarm persists after replacement: Verify connector seating, correct battery type/voltage, and clear alarms per the manual. Check for multiple battery locations (e.g., control + servo amp + robot base).
• Lost absolute position on a robot/axis: Perform mastering/calibration per procedure and investigate whether the swap occurred with power OFF or after a prolonged alarm.
• Memory loss after swap: Restore backups; re-enter parameters and offsets. Review the correct swap method for your model.
• Corrosion or leakage: Power down safely, clean or replace the harness, and install a new pack. Inspect yearly.

Environmental and Safety Notes

• Use UL/IEC-recognized cells where applicable.
• Do not short, crush, or expose to heat. Store and transport per lithium battery regulations.
• Recycle through approved e-waste or battery programs.

FAQ

Can I change a Fanuc battery with the power off?

Often no. Many Fanuc systems require the swap with main power ON to maintain memory. Check the manual for your exact controller/robot.

How often should I replace the battery?

Plan for annual replacement, or sooner if a low-battery alarm appears. Some CNC memory packs permit up to 24 months; follow your manual and plant PM policy.

Are generic batteries acceptable?

Use batteries that match the specified chemistry, voltage, capacity, and connector. Off-spec packs risk data loss and alarms. Genuine or OEM-approved equivalents are recommended.

What happens if the battery dies?

You may lose CNC parameters, offsets, programs, and/or robot mastering. Recovery can require reloading backups and re-mastering axes—plan backups and replace batteries proactively.

How do I identify the correct battery?

Check the controller/robot model tag and maintenance manual. Note voltage, chemistry, connector style, and pack configuration. Do not rely on visual similarity alone.

Always refer to the official Fanuc maintenance documentation for procedures and specifications specific to your model.