The Fanuc CNC battery is one of the most overlooked components in CNC machine maintenance — yet a dead battery can cause loss of all parameters, programs, and tool offsets, leading to costly downtime. This guide explains how to replace the Fanuc CNC battery correctly without losing your data.
Why Does Your Fanuc CNC Need a Battery?
The Fanuc CNC controller uses a lithium battery to retain critical data in memory (SRAM) when the machine is powered off. This includes:
- CNC parameters
- Machining programs (part programs)
- Tool offsets and work coordinate systems
- Pitch error compensation data
When the battery voltage drops, the controller displays a BAT alarm or Battery Low warning. At this point you must replace the battery as soon as possible — before switching off the machine — or risk losing all stored data.
Which Fanuc Battery Do I Need?
The most common Fanuc CNC battery is the A98L-0031-0025 — a 3V lithium battery used in Fanuc 0i, 16i, 18i, 21i, 30i, 31i, and 32i series controllers.
Other common Fanuc batteries include:
- A02B-0323-K102 — for Fanuc 30i/31i/32i Series
- A98L-0031-0007 — for older Fanuc controllers
Step-by-Step Battery Replacement Procedure
Important: Replace the battery with the machine POWERED ON to avoid data loss. SRAM data is retained as long as power is supplied.
- Obtain the correct replacement battery (A98L-0031-0025 or equivalent).
- Power ON the CNC machine and allow it to boot fully.
- Locate the battery on the controller (usually behind the front panel or on the main board).
- Note the battery connector orientation before removing.
- Disconnect the old battery and immediately connect the new battery.
- Do NOT leave the battery disconnected for more than 30 seconds.
- Power cycle the machine and verify the BAT alarm is cleared.
- Check that all parameters, programs, and offsets are intact.
What if I Already Lost My Data?
If the battery has fully discharged and data has been lost, you will need to:
- Restore parameters from a backup (RS232, SRAM card, or USB)
- Re-enter tool offsets and work coordinates
- Reload machining programs
This is why regular preventive maintenance — including battery checks — is so important. We recommend replacing the Fanuc CNC battery every 2-3 years as part of your AMC (Annual Maintenance Contract).
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We stock the A98L-0031-0025 Fanuc CNC battery at the best price in India. All batteries are genuine and tested before dispatch.
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