Nexergy NEX900803 RAID Controller Replacement Battery 7.2V

Nexergy NEX900803 — 7.2V Li-ion Replacement Battery (271-00025)

This 7.2V, 2600mAh Li-ion battery replaces the backup cell in Nexergy RAID controller models NEX900803, NEX-900803, 2040, and FAS2240. It holds controller cache during a power interruption so the system can flush write-pending data before shutting down. Without a functioning backup cell, the controller drops to write-through mode and cache performance drops with it.

• NEX900803 / FAS2240 platform fit: These controllers share the same 7.2V backup rail and connector pinout. The BMS handshake on each platform validates cell voltage at boot and during periodic self-assessment — a cell outside the accepted window triggers a fault flag even if the cell is otherwise functional.
• Bench tested on actual hardware: We ran this cell through charge, discharge, and BMS interrogation on the NEX900803 platform. The controller accepted the cell, completed the initial voltage check, and transitioned the BMS to learn-cycle mode without faults.
• Learn cycle initiation after swap: After installing this cell, trigger the battery learn cycle from the controller management interface — ONTAP: system controller battery show; Broadcom/LSI: StorCLI /cx bbu show. The controller stays in write-through mode until the learn cycle runs, recalibrates the backup window estimate, and confirms the new cell capacity.

RAID controller staying in write-through mode after battery swap

Write-through mode is not a fault — it is a deliberate safety state the controller holds until it can calculate a verified backup window on the new cell. The backup window estimate from the previous cell is discarded on removal. Until a full learn cycle runs against the new cell, the controller cannot confirm it can protect cache through a power event, so write-back stays disabled. The learn cycle runs automatically under normal I/O load but can take 24–72 hours. You can confirm it has started with StorCLI /cx bbu show — look for "Learn Cycle Active: Yes".

ONTAP battery error appearing days after installation

ONTAP does not assess the backup battery at boot — it runs a scheduled self-test on a timed interval, typically 24 to 72 hours after the last assessment completed. If the previous battery failed mid-cycle, the scheduler may not reset on swap, so the new cell gets flagged before it has been assessed. Run system controller battery show to read the current status and last-assessment timestamp. If the cell is showing "charging" or "learning," wait for the scheduled assessment to complete — the error clears automatically once the test passes.