Biolight M8000 Patient Monitor Replacement Battery 11.1V 3400mAh

Biolight M8000 / M9000 Series — 11.1V Li-ion Replacement Battery (LI1104C)

This 11.1V 3400mAh Li-ion battery replaces part number LI1104C (also listed as 12-100-0006) in Biolight patient monitors including the M8000, M9000, M9000A, and M9500. It powers the monitor's vital signs display — heart rate, SpO2, and blood pressure — when AC mains are unavailable or when the unit needs to move with a patient. Capacity is 3400mAh / 37.74Wh, matching the OEM specification.

• M8000 / M9000 / M9500 platform fit: These monitors share a common battery bay geometry, connector pinout, and BMS handshake protocol across the series. The same voltage rail (11.1V nominal, three-cell configuration) and communication lines run across all listed models, which is why one part number covers the full range.
• Bench tested on actual hardware: We ran charge and discharge cycles through the BMS and confirmed the protection circuit trips correctly at low-voltage cutoff. The BMS communication line responded normally — the monitor recognised the battery, completed its internal verification, and reported charge state without fault codes.
• Post-swap self-test protocol: After installing this battery, let the monitor complete its full power-on self-test cycle without interruption. The M8000 series runs a BMS verification routine at startup. Cutting power during this sequence causes a false battery fault flag that will persist until the next clean reboot.

Why the M8000 alarms low battery immediately after a confirmed full charge

The M8000 BMS stores a charge profile calibrated to the OEM cell's internal resistance and voltage curve. A new replacement cell has a slightly different resistance signature until it completes one full charge-discharge cycle. Until that cycle runs, the BMS applies a conservative threshold and can flag low battery even when the cell is at capacity. Run one full charge-discharge cycle before clinical use. After that cycle, the monitor's state-of-charge reading stabilises and the alarm clears.

Monitor will not power on after battery has been in storage

Li-ion cells self-discharge during storage. If a cell drops below approximately 2.5V per cell (7.5V total across a three-cell pack), the BMS enters deep-discharge protection and blocks output — the monitor sees no voltage and will not boot. Place the battery on charge for a minimum of 30 minutes before attempting to power on the monitor. Most BMS circuits recover and re-enable output once the cell voltage climbs back above the recovery threshold, typically around 8.0–9.0V for this pack configuration.