271-00027 NetApp NEX-90089 RAID Battery 7.2V 6800mAh Li-ion

NetApp NEX-90089 / FAS3240 — 7.2V Li-ion Replacement Battery (271-00027)

This 7.2V 6800mAh Li-ion cell replaces the backup battery in NetApp NEX-90089, FAS3240, and ES3259 RAID controller modules. It supplies emergency power to the controller cache during an unexpected power loss, giving the system time to flush write-pending data to disk. OEM part numbers 271-00027, 111-00750+A1, 111-00750+B0, and related revisions are all covered by this cell.

• NEX-90089 / FAS3240 / ES3259 platform fit: These three platforms share the same battery bay geometry, connector pinout, and BMS handshake protocol. The controller authenticates the cell through a timed learn cycle rather than a static ID check, so the replacement triggers the same recalibration sequence as the OEM unit.
• Bench tested on actual hardware: We cycled this cell through full charge and controlled discharge on a RAID controller bench rig. The BMS accepted the cell without fault, held float charge correctly, and reported a stable backup window estimate after the learn cycle completed.
• Post-swap learn cycle initiation: After fitting this battery, the controller stays in write-through mode until it completes a full learn cycle. In ONTAP, run system controller battery show to monitor status. On Broadcom/LSI managed systems, use StorCLI /cx bbu show. Expect 24–72 hours before the controller transitions back to write-back mode.

RAID controller staying in write-through mode after battery swap

Write-through mode is not a fault — it is the controller's default safe state when the backup window has not been confirmed for the installed cell. After a battery swap, the controller must run a full learn cycle to measure the new cell's actual capacity and calculate how long it can sustain cache power. Until that cycle completes, the controller refuses to enable write-back caching regardless of the battery's charge level. On ONTAP systems, system controller battery show will display the learn cycle progress and estimated completion time.

ONTAP reporting a battery error days after installation

ONTAP schedules battery assessment on a timed interval, not at boot, so a fault flag can appear 48–96 hours after the swap even when the cell is functioning correctly. If the learn cycle has not yet completed when the scheduled assessment runs, ONTAP logs it as a failed assessment. Check the output of system controller battery show — if the learn cycle is still in progress, the error clears automatically once the cycle finishes. If the error persists after a completed learn cycle, verify the cell voltage is within the 7.2V nominal range before escalating.