Marquette Mac 12 Recorder 3.6V Ni-MH Replacement Battery 401086-002

Marquette Mac 12 / Mac 15 Recorder — 3.6V Ni-MH Replacement Battery (401086-002)

This is a 3.6V, 1100mAh Ni-MH replacement battery for the Marquette Mac 12 and Mac 15 Recorders, plus the 15 and 16 Central Console units. It matches OEM part numbers 401086-002, B11129, 5653, and B10068. The cell fits the original battery bay without modification and connects to the device BMS directly.

• Mac 12, Mac 15, and Central Console compatibility: These four Marquette devices share the same 3.6V Ni-MH voltage rail, connector pinout, and BMS communication protocol — so one cell covers the full platform. The BMS in each unit reads cell chemistry and capacity the same way, and this battery passes that handshake on all four.
• Bench tested on actual hardware: We ran this cell through charge and load cycles on a Mac 12 unit. The BMS accepted the cell without error flags, completed its self-test sequence, and held stable voltage under the recorder's continuous ECG acquisition load. No BMS trip or fault codes were logged.
• Post-swap self-test protocol: After installing this battery, let the Mac 12 or Mac 15 complete its full power-on self-test without interruption. Cardiac recorders run a BMS verification pass at startup — cutting power during this sequence triggers a persistent false battery fault that does not clear until the device is fully rebooted and the self-test completes cleanly.

Why the Mac 12 alarms low battery on a freshly charged replacement cell

The Mac 12 BMS uses a capacity threshold calibrated to an OEM cell that has completed at least one full charge-discharge cycle. A brand-new Ni-MH cell has not yet reached its rated capacity curve, so the BMS reads the initial charge state as below threshold and triggers the low battery alarm. This is not a fault with the replacement cell — it is the BMS comparing an unconditioned cell against a reference it expects to be fully characterised. Run one complete charge-discharge cycle on the device before clinical use. After that cycle, the BMS recalibrates and the alarm clears.

Mac 12 will not power on after the battery sat in storage

Ni-MH cells self-discharge at roughly 1–3% per day at room temperature. A cell stored for several weeks can drop below the BMS recovery threshold — typically around 3.0V for this platform — at which point the device refuses to boot rather than risk operating on an unstable supply during ECG acquisition. Place the battery on charge for a full uninterrupted cycle before attempting to power the unit. If the charge indicator does not advance within 30 minutes, check that the charger output is delivering at least 4.2V at the battery terminals before assuming the cell is faulty.