ECG-901B Replacement Battery 12V 2000mAh Ni-MH Medical

Spring ECG-901B — 12V Ni-MH 2000mAh Replacement Battery

This is a 12V 2000mAh Ni-MH replacement battery for the Mindray ECG-901B portable electrocardiograph. It fits the ECG-901B directly and matches the original cell's voltage rail and connector format. Capacity is 2000mAh (24Wh) as specified for this platform.

• ECG-901B platform fit: The Mindray ECG-901B uses a 12V Ni-MH cell with a specific BMS handshake tied to charge termination voltage and thermal cutoff thresholds. This cell matches that voltage rail and connector, so the device charge circuit recognises it correctly without fault codes.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the ECG-901B platform. The BMS accepted the cell, charge termination triggered at the correct delta-V point, and the device completed its power-on self-test without flagging a battery fault.
• First-use self-test protocol: After installing this battery, let the ECG-901B complete its full power-on self-test without interruption. The device runs a BMS verification sequence at startup — cutting power during this window logs a persistent battery fault that won't clear until the next complete boot cycle.

Why the ECG-901B charge indicator stalls below 100% on a new cell

The ECG-901B charge IC applies a conservative current limit when it detects an unfamiliar impedance signature from a new Ni-MH cell. On the first charge, the IC holds back until the cell's internal resistance drops into the expected range after initial cycling. This causes the charge indicator to plateau at 85–95% and sit there longer than expected. Run one full charge-discharge cycle and the indicator will reach 100% normally on the second charge.

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

Ni-MH cells self-discharge at roughly 1–3% per day under storage conditions. If the battery shipped or sat on a shelf for several weeks, terminal voltage can fall below the ECG-901B's BMS recovery threshold — typically around 10.5V for a 12V Ni-MH pack. The device will refuse to boot rather than draw from a cell that low. Connect the charger and leave it on a full charge cycle before attempting power-on; the BMS will reinitialise once voltage recovers above 11V.