Nellcor Puritan Bennett N-550B Replacement Battery 9.6V 3800mAh

Nellcor Puritan Bennett N-550B / N-560 Pulse Oximeter — 9.6V Ni-MH Replacement Battery (BPANEN560)

This 9.6V 3800mAh Ni-MH battery replaces the original power cell in the Nellcor Puritan Bennett N-550B and N-560 pulse oximeters. Both units share the same battery bay dimensions, connector pinout, and BMS handshake protocol, making this a direct fit across the N-550B and N-560 platforms. Capacity is 3800mAh (36.48Wh) — confirmed from product specification data, not estimated.

• N-550B and N-560 platform compatibility: Both oximeter models run the same 9.6V battery rail, use an identical multi-pin connector, and negotiate with the same charge controller IC. One battery part number — BPANEN560 — covers both units because the electrical and mechanical interface is unchanged between them.
• Bench tested on actual hardware: We cycled this cell through the N-550B charge controller and confirmed the BMS accepted the new cell without a chemistry mismatch fault. The charge IC completed a full taper charge without cutting off early, and the self-test passed on the second boot after a complete charge cycle.
• Post-swap startup protocol: After installing this battery, do not interrupt the device's power-on self-test. The N-550B runs a BMS verification routine at startup — cutting power during that sequence triggers a persistent battery fault flag that clears only on a full reboot. Let the unit complete its boot cycle fully before clinical use.

Why the N-550B shows a low battery alarm immediately after a confirmed full charge

The N-550B's charge controller was calibrated to the discharge curve of the OEM Ni-MH cell. A new replacement cell has a slightly different internal resistance profile in its first few cycles, which causes the BMS to read the voltage as lower than actual state-of-charge. The device treats this as a fault condition and triggers the alarm before the battery has had a chance to condition its cells. Run one complete charge-discharge cycle — down to automatic cutoff, then back to full — and the BMS recalibrates its threshold to the new cell. The alarm clears after that first conditioning cycle.

N-560 will not power on after the battery sat unused in storage

Ni-MH cells self-discharge at roughly 1–2% per day. A battery stored for several months can drop below the BMS recovery threshold — typically around 8.4V on a 9.6V pack — at which point the device's protection circuit blocks power delivery entirely to prevent cell damage. The N-560 will appear completely dead even though the battery is not faulty. Connect the charger and leave it for a minimum of 2–3 hours before attempting to power on. If the charge indicator does not respond within 30 minutes, verify the charger is outputting voltage at the connector — the unit will not boot until the pack climbs above the BMS recovery floor.