About this replacement
Alaris Medicalsystems Infusion Pump 231/531 — 12V Ni-MH Replacement Battery (125-00-444900968)
This 12V 1800mAh Ni-MH battery replaces OEM part 125-00-444900968 in the Alaris Medicalsystems Infusion Pump 231 and Infusion Pump 531. These pumps deliver IV fluids and medications under controlled flow rates, so a failed or degraded battery is a direct clinical concern. Capacity is 1800mAh (21.6Wh) — matching OEM specification.
- Infusion Pump 231 and 531 compatibility: Both models share the same 12V battery rail, connector pinout, and BMS handshake protocol. The 125-00-444900968 part number covers both variants — no adapter or wiring change needed.
- Bench tested on actual hardware: We cycled this cell through the pump's power-on self-test sequence and monitored BMS communication. The charge IC accepted the cell without fault codes on the first full charge cycle.
- Power-on self-test after installation: After fitting the battery, allow the pump to complete its full startup self-test without interruption. The BMS runs a verification check at boot — cutting power during this window causes a false battery fault that persists until the next complete reboot cycle.
Self-test failure after battery swap on the Infusion Pump 531
The Pump 531's BMS runs a cell-verification routine at every startup. A fresh Ni-MH cell that hasn't completed at least one full charge-discharge cycle may sit slightly below the BMS acceptance threshold, triggering a self-test fault. This is a BMS learn-cycle issue, not a dead cell. Run one complete charge from flat to full, then reinstall and allow the pump to complete its boot sequence before clinical use.
Charge indicator not reaching 100% on the first charge after installation
The Alaris pump's charge IC applies a conservative current limit when it first reads a new Ni-MH cell — particularly one that has self-discharged during storage. The controller reads the lower open-circuit voltage and caps the charge rate until it builds a history with the cell. Run a full first charge uninterrupted; the cell should reach 12V resting voltage and the indicator should complete normally on the second cycle. If resting voltage remains below 11.5V after a full charge, check the charger contacts for oxidation before replacing the cell.