About this replacement
Dell PowerEdge 1850 / 2800 / 2850 — 3.7V Li-ion RAID Controller Battery (G3399)
This is a 3.7V 1250mAh lithium-ion replacement for the Dell G3399 RAID controller cache battery. It fits the PowerEdge 1850, 2800, and 2850 servers. The battery backs the controller's volatile write cache during unexpected power loss, holding data until the controller can flush safely to disk.
- PowerEdge 1850 / 2800 / 2850 shared platform: These three server generations use the same RAID controller board and G3399 battery footprint. The connector pinout, BMS handshake voltage thresholds, and physical dimensions are identical across all three — one cell fits the entire group.
- Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle and verified the BMS accepted the cell without fault codes. The controller transitioned from write-through to write-back mode once the backup window estimate cleared the controller's minimum threshold.
- Learn cycle required after swap: After fitting this battery, initiate the learn cycle from your controller management interface — StorCLI: /cx bbu show. The controller stays in write-through mode until the learn cycle completes and recalibrates the backup window against the new cell's actual capacity. Skipping this step leaves cache protection inactive.
RAID controller stuck in write-through mode after battery swap
The controller switches to write-through automatically when it detects a new cell with no calibrated backup window. It does not switch back to write-back on its own just because the battery reads as charged. The learn cycle — a controlled full discharge and recharge — is what generates the backup window estimate the controller trusts. On the PowerEdge 1850 with a Broadcom/LSI controller, trigger the learn cycle via StorCLI and expect the transition to write-back within 24–48 hours under normal server load.
Management console showing a battery error days after installation
Dell's RAID controller firmware runs its battery self-assessment on a timed schedule — not at boot and not immediately after a swap. If the assessment window falls two or three days after installation and the learn cycle has not yet completed, the controller logs a battery fault because it cannot confirm a valid backup window. This is a sequencing issue, not a faulty cell. Check the learn cycle status first using StorCLI /cx bbu show; if the cycle is still running, the error will clear once it finishes and the backup window figure is written to controller memory.