Edan M9 Patient Monitor Replacement Battery 14.4V 6800mAh

Edan M9 / M8A Series — 14.4V Li-ion Replacement Battery (HYLB-957A)

This 14.4V 6800mAh Li-ion battery replaces the HYLB-957A and HYLB-957 cells used in the Edan M9, M9B, and M8A portable patient monitors. These monitors run ECG, SpO2, NIBP, and temperature simultaneously — the battery supports that full sensor load. Voltage and capacity match OEM specifications exactly.

• M9, M9B, and M8A compatibility: All three models share the same battery bay dimensions, 14.4V nominal rail, and BMS communication protocol. The connector is identical across the series, and the pack's protection circuit matches the charge termination logic the M9 platform expects.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on an M9 unit. The BMS completed cell balancing without flagging an incompatible chemistry error, and the monitor's battery status indicator updated correctly through each stage.
• Post-swap self-test requirement: After installing this battery, let the M9 complete its full power-on self-test without interruption. The device runs a BMS verification sequence at startup — cutting power during this cycle triggers a false battery fault that sticks until the next clean reboot.

Why the M9 alarms low battery immediately after a confirmed full charge

The M9's BMS compares cell voltage and internal resistance readings against a learned profile from the previous pack. A new cell has slightly different impedance characteristics, even at full charge, so the monitor flags it as low until it builds a baseline. This is not a defective battery — it is the device's protection logic reacting to an unfamiliar cell signature. Run one complete charge-discharge cycle, then recharge fully. After that cycle, the BMS recalibrates its threshold and the alarm clears.

M9 will not power on after the replacement battery sat in storage

Li-ion cells self-discharge at roughly 2–3% per month in storage. If the pack sat long enough, cell voltage can drop below the M9's minimum boot threshold — typically around 12V for a 14.4V nominal pack — and the BMS blocks output to prevent damage. The monitor will show nothing when you press power. Connect the battery to the M9 charger for at least 30 minutes before attempting to power on; this brings the cell voltage above the recovery floor and allows the BMS to re-enable the output path.