ADE M400020 Medical Scale Compatible Battery 3.7V 5200mAh

ADE M400020 Chair Scale — 3.7V Li-ion Replacement Battery (MZ40013-002)

This is a 3.7V, 5200mAh Li-ion replacement battery for the ADE M400020 chair scale. It restores power to the scale's display and body composition measurement functions when the original cell has depleted. The OEM part number is MZ40013-002.

• M400020 chair scale compatibility: The M400020 uses a single-cell Li-ion architecture at 3.7V nominal. This replacement matches that voltage rail, connector pinout, and BMS handshake requirements so the scale's charge IC recognises the cell correctly on first insertion.
• Bench tested on actual hardware: We ran this cell through the M400020's power-on sequence and monitored BMS communication. The charge IC accepted the cell, completed its initialisation handshake, and the self-test sequence cleared without a battery fault flag.
• Post-swap self-test protocol: After installing this battery, let the M400020 complete its full power-on self-test without interruption. The device's BMS runs a verification cycle at startup — cutting power during this sequence logs a false battery fault that persists until the next clean reboot.

Why the M400020 alarms low battery immediately after a confirmed full charge

The M400020's BMS uses a learned capacity threshold calibrated to the OEM cell's chemistry profile. A new replacement cell hasn't completed a full charge-discharge cycle, so the BMS has no baseline to reference and defaults to a conservative low-battery flag. This isn't a fault in the replacement cell — it's the BMS running without calibration data. One complete charge-discharge cycle gives the BMS enough data to set the correct threshold, and the low-battery alarm clears on subsequent use.

Scale won't power on after the replacement cell sat in the package

Li-ion cells self-discharge during storage. If the cell voltage drops below approximately 2.5V, the M400020's BMS enters a protection state and blocks normal power-on to prevent damage to a deeply discharged cell. Plug the scale into its charger and leave it connected for at least 30 minutes before attempting to power on — the charge IC applies a low-current pre-charge trickle at this voltage range. Once the cell recovers above 3.0V, the BMS exits protection and the scale powers on normally.