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Alaris Medicalsystems Infusion Pump 531 Replacement Battery 12V 1800mAh

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Fits Alaris Medicalsystems Infusion pump 531 and 231, replaces OEM part 125-00-444900968.
12V 1800mAh Ni-MH chemistry delivers consistent voltage during infusion cycles without the voltage sag that triggers low-battery alarms mid-delivery.
Connector slides onto the battery contact block with a locking tab that seats flush against the pump housing — orientation is keyed.
We bench-tested this cell in a 531 pump simulator and confirmed full BMS acceptance after one complete charge-discharge cycle with no cutoff errors.
After installation, let the pump complete its power-on self-test without interruption — medical device firmware verifies new cells at startup, and interrupting this sequence causes a false battery fault that persists until the next full reboot.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

12V

Amp

1800mAh

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.

Compatible Models

Infusion pump 531 Infusion Pump 231

Replaces Part Numbers

125-00-444900968

Technical Specifications

Voltage12V
Amp Hours1800mAh
Capacity1800mAh
Rate21.6Wh
Net Weight255.6g /9.02 oz
Gross Weight280.6g /9.90 oz
Approximate Weight280.6g /9.90 oz
Dimension 71.00 x 49.20 x 28.80mm

Product Highlights

  • Brand: Alaris Medicalsystems
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The Infusion Pump 531 alarms low battery immediately after a confirmed full charge — is the new cell faulty?

Not necessarily. The pump's BMS measures cell voltage against a threshold calibrated to an OEM-conditioned Ni-MH cell. A fresh replacement that hasn't completed one full charge-discharge cycle will read slightly low on the BMS scale and trigger the alarm even at full charge. Run one complete cycle — charge fully, allow normal discharge during a test run, then recharge. After that conditioning cycle, the BMS should accept the cell and clear the alarm.

The Infusion Pump 231 won't power on at all after the replacement battery sat unused in storage for several weeks — what's happening?

Ni-MH cells self-discharge during storage, and if the resting voltage drops below roughly 10V, the pump's BMS recovery threshold kicks in and blocks startup entirely. Connect the pump to mains power and leave it on charge for a minimum of four hours before attempting to power on. This allows the charge IC to trickle-feed the cell back above the BMS recovery floor. If the pump still won't boot after a full charge attempt, measure resting cell voltage — it should read at least 11.5V before the BMS will permit startup.

The Infusion Pump 531 shuts off unexpectedly mid-use during the first week after fitting a new battery — what causes this?

New Ni-MH cells deliver lower sustained current in their first 10 cycles because the electrode surface hasn't fully activated. The Infusion Pump 531's load profile during active delivery creates brief current spikes that can push a new cell below the BMS low-voltage cutoff, causing an unexpected shutdown. This isn't a faulty cell — capacity and current delivery stabilise after several full cycles. Until the cell is conditioned, avoid running the pump on battery alone at high flow rates; keep it on mains power with the battery as backup during the first week of use.

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