About this replacement
Masimo SEDLine — 11.1V Li-ion Replacement Battery (5139-0004)
This is a 11.1V, 2600mAh Li-ion battery for the Masimo SEDLine patient monitor. The SEDLine measures brain activity and depth of anesthesia in surgical and critical care settings. This cell replaces OEM part 5139-0004 and fits the standard battery bay on the SEDLine unit.
- SEDLine platform fit: The SEDLine runs a fixed 11.1V three-cell Li-ion pack architecture. The BMS on this unit negotiates with the host device over a dedicated communication line — the connector pinout and cell voltage range must match the OEM spec or the monitor will reject the pack at startup.
- Bench tested on actual hardware: We cycled this pack through charge and discharge under a load profile matching the SEDLine's active monitoring draw. The BMS completed its verification handshake and the monitor accepted the pack without faulting. Cell balancing across all three cells stayed within tolerance through the first three cycles.
- Post-swap self-test protocol: After installing this battery, allow the SEDLine to complete its full power-on self-test without interruption. The device runs BMS verification at startup — cutting power during this sequence triggers a false battery fault that will persist until the next clean reboot, not until the next charge.
Why the SEDLine rejects a new battery pack at startup
The SEDLine BMS uses a learn cycle to validate a new cell's discharge curve against stored OEM parameters. On a fresh pack, the BMS has no prior cycle data to reference, so some units flag the battery as unverified and refuse to boot on it. This is a firmware-side protection, not a hardware fault with the battery. Running one complete charge-to-discharge cycle allows the BMS to record the cell's actual capacity curve and clear the rejection flag.
Charge indicator stuck below 100% after first full charge
On the first charge, the SEDLine's charge IC applies a conservative current limit to a pack it has not previously profiled. This causes the charge cycle to terminate early at around 90–95% by the monitor's internal gauge, even though the cells have accepted a full charge. The percentage display catches up after one full discharge and recharge cycle, once the BMS recalibrates its state-of-charge calculation against the actual cell capacity. Do not interrupt the second charge — let it run to automatic termination.