Medtronic Laryngoscope Mac Video 3.6V Replacement Battery 340-000-000

Medtronic McGrath MAC / Laryngoscope Mac Video — 3.6V Li-SOCl2 Replacement Battery (340-000-000)

This is a 3.6V, 800mAh lithium-thionyl chloride cell replacing OEM part 340-000-000. It fits the Medtronic McGrath MAC and Laryngoscope Mac Video EACH video laryngoscopes used in airway management and intubation procedures. Voltage and chemistry must match exactly — Li-SOCl2 is not interchangeable with Li-ion or alkaline cells in this device.

• McGrath MAC and Mac Video compatibility: Both models share the same battery bay geometry, voltage rail, and BMS handshake protocol. The 340-000-000 cell satisfies the BMS verification routine on both platforms without modification.
• Bench tested on actual hardware: We ran this cell through the McGrath MAC power-on sequence and confirmed the BMS accepted the cell without fault codes. The self-test completed normally and video output activated within the standard boot window.
• Post-installation self-test protocol: After fitting this cell, let the device complete its full power-on self-test without removing or cycling the battery. Interrupting the BMS verification sequence during startup triggers a persistent false battery fault that does not clear until the device is fully rebooted with the cell seated.

Why the McGrath MAC reports a battery fault after a fresh cell installation

The McGrath MAC BMS runs a chemistry verification check at startup. Li-SOCl2 cells have a slightly elevated internal resistance when new, which can cause the BMS to flag a marginal battery state on the first boot. This is not a faulty cell — it is the BMS reading a new cell against thresholds calibrated for a cell that has already completed one charge-discharge cycle. Running one full operational cycle before clinical deployment clears the threshold mismatch and the fault does not return.

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

Li-SOCl2 cells self-discharge slowly in storage and can drop below the McGrath MAC's BMS recovery threshold if left unseated for an extended period. When voltage falls below that floor, the BMS will not initiate the boot sequence — the device appears completely dead. Fit the cell and connect the device to its charger for a minimum of 30 minutes before attempting to power on. If the device still does not respond, check cell voltage directly with a multimeter — a reading below 3.0V indicates the cell requires recovery charging before the BMS will accept it.