About this replacement
IBM AS400 RAID Controller — 3.6V Ni-MH Replacement Battery (44L0313)
This 3.6V, 2000mAh Ni-MH battery backs the write cache on IBM AS400 and iSeries RAID controller cards. It holds the controller's cache memory during a power loss or system shutdown, preventing data corruption on in-flight writes. Compatible with AS400, AS400 i5, AS2740, and iSeries controllers using OEM part numbers 44L0313, 42R5070, 22R2717, and related variants.
- AS400 and iSeries RAID controller fitment: These controllers share the same 3.6V NiMH cell format, connector pinout, and BMS handshake across the AS400, AS400 i5, AS2740, and iSeries lines. IBM standardised this cell across multiple card revisions, which is why the OEM cross-reference list spans part numbers 2763, 2778, 2782, 5703, 5709, and 5729.
- Bench tested on actual hardware: We ran this cell through charge-discharge cycles and monitored the BMS handshake. The controller detected the new cell, initiated a learn cycle, and transitioned from write-through to write-back mode once the backup window was recalibrated against the new capacity.
- Post-swap learn cycle initiation: After installing this battery, kick off a manual learn cycle from the controller management interface — on iSeries use the Hardware Management Console battery conditioning function. The controller cannot accurately estimate its backup window until it completes at least one full learn cycle on the new cell, and it will hold in write-through mode until that recalibration finishes.
RAID controller staying in write-through mode after battery swap
After a battery replacement, the AS400 RAID controller defaults to write-through mode as a safety measure — it does not automatically trust the new cell's backup window. The controller must complete a full learn cycle before it will re-enable write-back caching. This cycle discharges and recharges the cell under normal operating load, measuring actual capacity rather than relying on a nominal value. Depending on system load, this takes 24 to 72 hours; the controller switches to write-back mode automatically once the cycle reports a sufficient backup window.
Management console reporting a battery fault days after installation
The AS400 controller runs its battery self-assessment on a timed interval — not at boot and not immediately after a swap. If the scheduled assessment fires before the learn cycle has completed, the controller logs a battery fault because the backup window estimate is still undefined or below threshold. This is expected behaviour, not a cell defect. Allow the learn cycle to complete fully, then check the battery status again via the Hardware Management Console; the fault clears once the controller has a valid backup window reading above its minimum threshold — typically 25 seconds at 3.3V load.