About this replacement
Masimo Rad-97 Pulse Oximeter — 3.8V Li-Polymer Replacement Battery (377728)
This 3.8V 4500mAh Li-Polymer battery replaces the internal power cell in the Masimo Rad-97 pulse oximeter. It fits the Rad-97 series used in clinical and home patient monitoring settings. Capacity matches the original 17.1Wh specification listed in the product data.
- Rad-97 series fit: The Rad-97 platform uses a single internal Li-Polymer cell at 3.8V with a specific connector and BMS handshake tied to OEM part numbers 377728, 27058, and 99013. All three cross-reference the same cell form factor and voltage rail, so this replacement covers the full Rad-97 lineup without modification.
- Bench tested on actual hardware: We cycled this cell through the Rad-97 charge controller and confirmed the BMS accepted the new cell, completed charge termination correctly, and did not flag a battery fault during post-charge self-test. Capacity read-back settled to full after the second charge cycle.
- Post-swap power-on protocol: After fitting this battery, let the Rad-97 complete its full power-on self-test without interruption. The device runs BMS verification at startup. Cutting power during that sequence triggers a false battery fault that persists until the next clean reboot.
Device not completing boot sequence after battery installation
The Rad-97 runs a BMS learn cycle during its first boot on a new cell. If the cell voltage sits below approximately 3.5V from storage discharge, the charge controller may refuse to initiate a full charge and the device stalls at the boot screen. Connect the device to mains power before pressing the power button. Let the charger bring the cell up for at least 20 minutes before attempting a cold boot. This gives the BMS enough voltage headroom to pass its startup threshold.
Low battery alarm firing immediately after a confirmed full charge
This happens because the Rad-97's BMS applies an OEM-calibrated charge threshold that a new cell hasn't yet verified through its internal resistance profile. On the first one or two cycles, the BMS reports capacity conservatively and triggers the low battery alarm before actual depletion. Run one complete charge-discharge cycle under normal monitoring load before clinical deployment. After that cycle, the BMS recalibrates its capacity estimate and the alarm threshold aligns correctly with actual cell state.