McGrath 340-000-000 Replacement Battery 3.6V 800mAh

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

This 3.6V, 800mAh Li-SOCl2 cell replaces the OEM battery in the McGrath MAC Video Laryngoscope (Part No. 340-000-000). It powers the device's integrated video system, including the camera and display circuitry used during airway visualization. Li-SOCl2 chemistry is standard for this class of medical device — it holds voltage flat across discharge and tolerates the long storage intervals common in clinical equipment.

• McGrath MAC platform fit: The MAC Video Laryngoscope runs a 3.6V single-cell architecture. The BMS expects a Li-SOCl2 discharge curve — not Li-ion — so substituting a different chemistry triggers false low-battery flags or prevents the device from completing its self-test sequence.
• Bench tested on actual hardware: We ran this cell through the MAC laryngoscope's power-on sequence and confirmed the BMS accepted the battery without fault codes. The self-test completed cleanly and the video system initialized normally on first boot.
• Post-swap self-test protocol: After installing this cell, let the device complete its full power-on self-test without interrupting it. The BMS runs a verification pass at startup. Powering down mid-sequence causes a false battery fault that persists until the next complete reboot cycle.

Why the MAC laryngoscope reports low battery immediately after a fresh cell install

The MAC's BMS uses a stored discharge profile to judge cell state. A new Li-SOCl2 cell has not yet established that profile, so the BMS can flag it as low even when voltage is at or above 3.6V. This clears after one full charge-discharge cycle, which gives the BMS enough data to set its threshold correctly. Do not use the device clinically until that first cycle is complete and the self-test passes without fault.

MAC laryngoscope not powering on after the battery sat unused in storage

Li-SOCl2 cells self-discharge slowly during storage, but if the voltage drops below the BMS recovery threshold — typically around 3.0V — the device may refuse to power on at all. The BMS interprets this as a dead or absent cell. Place the battery in a compatible charger and allow a slow recovery charge before reinserting it. If the device still does not boot after recovery, check open-circuit voltage at the terminals — anything above 3.2V should clear the BMS lockout on next insertion.