Palco Laboratories 400 Replacement Battery 12V 2000mAh

Palco Laboratories 400 / 500 Pulse Oximeter — 12V Ni-MH Replacement Battery (5781)

This is a 12V, 2000mAh Ni-MH replacement battery for the Palco Laboratories Model 400 and 500 Pulse Oximeters. Part number 5781 matches the OEM specification for voltage, chemistry, and connector. It restores power to portable pulse oximeter units used in clinical and home healthcare settings when the original cell has degraded past usable capacity.

• Model 400 and 500 platform fit: Both the 400 and 500 Pulse Oximeter units share the same 12V battery bay, connector pinout, and BMS handshake protocol — which is why a single part number covers both. Swapping between models does not require any adapter or wiring change.
• Bench tested on actual hardware: We cycled this cell through a full charge-discharge sequence and monitored BMS communication. The charge IC accepted the cell without fault flags, and the protection circuit held within the expected cutoff thresholds for Ni-MH chemistry at this voltage rail.
• Post-installation self-test protocol: After fitting this battery, allow the device to complete its full power-on self-test without interruption. The Model 400 runs a BMS verification routine at startup — cutting power mid-sequence causes a false battery fault that persists until the next complete reboot cycle.

Why the Model 400 charge indicator stalls before reaching 100% on a new cell

Ni-MH charge ICs on medical devices apply a conservative delta-V cutoff algorithm on the first charge cycle. A new cell has not yet established a stable internal resistance baseline, so the IC interprets the flat voltage plateau as a full-charge signal earlier than expected. This is not a fault — it resolves after one complete charge-discharge cycle. After that first conditioning cycle, the charge IC recalibrates and the indicator will reach full charge normally.

Device will not power on after battery sat in storage

Ni-MH cells self-discharge during storage — if a replacement cell has been sitting unused, it may drop below the BMS recovery threshold before it ever reaches the device. The Model 400's BMS will refuse to initialise if it reads below approximately 10.8V at the battery terminals. Place the battery on the charger for a minimum of 30 minutes before attempting to power on the device. If the charge indicator shows no activity after 30 minutes, check terminal contact alignment inside the battery bay.