Maico easyTymp Replacement Battery 3.7V 1800mAh MAI-721-4

Maico easyTymp / Interacoustics Titan — 3.7V Li-ion Replacement Battery (MAI-721-4)

This 3.7V Li-ion cell (1800mAh / 6.66Wh) replaces the internal battery in the Maico easyTymp tympanometer and the Interacoustics Titan and TCallisto diagnostic systems. All three devices share the MAI-721-4 / 74101501 cell platform and the same connector footprint. Capacity comes from the product specification — 1800mAh at 3.7V nominal.

• Cross-platform fit — easyTymp, Titan, TCallisto: These three clinical tympanometers share an identical battery bay, connector locking tab, and BMS handshake protocol. The same cell powers all three because the voltage rail and charge IC requirements match across the platform.
• Bench tested on actual hardware: We cycled this cell through the easyTymp charge sequence and confirmed the BMS accepted the cell, cleared the charge flag, and reported full capacity on the status screen. No error codes were thrown on first or second cycle.
• Post-installation self-test protocol: After fitting this cell, allow the device to complete its full power-on self-test without interruption. The BMS runs a verification pass at startup — cutting power during this sequence causes a false battery fault that persists until the next clean reboot.

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

The easyTymp's charge IC is calibrated to the OEM cell's internal resistance profile. A new replacement cell has a slightly different impedance signature on the first few cycles, which the BMS can interpret as insufficient charge even when the cell is at full voltage. This is a learn-cycle issue, not a cell defect. Run one complete charge-to-discharge-to-charge cycle before clinical use — after that, the BMS recalibrates its threshold and the alarm clears. Nominal full-charge voltage for this cell is 4.2V.

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

Li-ion cells self-discharge during storage. If the cell voltage has dropped below approximately 3.0V, the easyTymp's BMS will refuse to boot — this is a protection cutoff, not a faulty cell. Connect the device to the OEM charger and leave it for a minimum of 30 minutes without attempting to power on. The charge IC applies a low-current pre-charge trickle to recover cells below the cutoff threshold before switching to the main charge rate. Once the cell climbs above 3.0V, the BMS releases the lockout and the device boots normally.