About this replacement
Fanuc ISV ALPHA Series — 3V Li-MnO2 Replacement Battery (A02B-0323-K102)
This 3V, 1750mAh lithium-manganese dioxide cell replaces the backup battery in Fanuc ISV ALPHA, BETA ISV, BETA iSVSP, and related servo drive controllers. Its sole job is to hold SRAM contents and keep the real-time clock running when mains power is cut. Voltage and capacity match OEM part A02B-0323-K102 and the alternate A98L-0031-0028 (old version) exactly.
- ISV ALPHA and BETA ISV platform fit: These drives share the same 3V backup rail, SRAM retention circuit, and physical cell bay. One cell spec covers the full group because the BMS handshake is not involved — voltage threshold alone triggers the battery alarm in the controller firmware.
- Bench tested on actual hardware: We ran this cell against the retention circuit under load. Open-circuit voltage came in at 3.0V. The controller cleared its battery alarm within two minutes of installation and confirmed SRAM contents intact.
- Hot-swap procedure for ISV ALPHA controllers: Always replace this cell with the controller powered on and in RUN mode. The SRAM has no secondary hold capacitor on these drives — removing the battery while the controller is off will erase program memory and parameters immediately. If a cold swap occurred, reload the full program from the programming device before attempting a run.
Why the ISV ALPHA battery alarm does not clear after a confirmed good installation
On Fanuc servo drives, the battery alarm flag is written to a status register in firmware — it does not self-clear when a new cell is detected. After fitting the new cell, you must navigate to the alarm history in the controller's parameter screen and perform a manual alarm reset. Some ISV ALPHA firmware versions also require a single power cycle after the reset command before the alarm extinguishes on the front panel. If the alarm persists past that, check that the cell is seated fully — the contact springs on these drives are stiff and a partially seated cell will read as absent.
New cell reading below 3V on the controller's battery monitor screen
Li-MnO2 cells ship at a storage voltage that can sit 50–100mV below their nominal rated voltage. This is normal — the cell is not defective. Once installed, the controller's float circuit brings the reading up to full voltage within a few hours. If the monitor still shows below 2.8V after four hours on a powered controller, reseat the cell and check the contact pins for corrosion. A confirmed good cell should stabilise at or above 3.0V on the monitor screen.