Datex Volume Monitor 5400 Replacement Battery 4.8V 3600mAh

Datex Volume Monitor 5400 Series — 4.8V Ni-MH Replacement Battery

This is a 4.8V, 3600mAh Ni-MH replacement battery for the Datex Volume Monitor 5400, 5410, 5420, and 6800. These portable respiratory monitors use this cell pack to power the unit during patient assessments and clinical transport. Voltage, capacity, and connector match the original specification.

• Volume Monitor 5400 / 5410 / 5420 / 6800 fit: All four models share the same 4.8V battery bay, connector pinout, and BMS communication protocol. The charge circuit across this series treats cell voltage identically, so one cell pack covers the full platform.
• Bench tested on actual hardware: We ran this battery through a full charge cycle on a Volume Monitor 5400 and confirmed the BMS accepted the cell, completed its charge termination at the correct delta-V cutoff, and cleared the low-battery flag without fault codes.
• Post-swap self-test protocol: After installing this battery, let the monitor complete its full power-on self-test without interruption. The device runs a BMS verification sequence at startup — cutting power during this window triggers a false battery fault that persists until a clean reboot is performed.

Why the Volume Monitor 5400 alarms low battery immediately after a confirmed full charge

The 5400's charge IC uses a delta-V detection algorithm calibrated to the impedance signature of a conditioned OEM cell. A new Ni-MH cell has higher internal resistance and a flatter charge curve, so the IC under-reports state of charge on the first cycle. The BMS sets a fault flag when measured voltage doesn't match expected capacity at termination. One full charge-discharge cycle re-calibrates the threshold and clears the alarm. Charge to full, run the monitor under normal clinical load until the low-battery indicator triggers naturally, then recharge — the alarm will not recur.

Volume Monitor not completing boot sequence on a new battery

Ni-MH cells self-discharge during storage and can drop below 4.0V before installation. The 5400's BMS has a recovery threshold — if cell voltage is too low at power-on, the boot sequence halts before the self-test completes. Connect the monitor to mains power first and allow the charge circuit to bring the pack above 4.4V before attempting a standalone boot. If the unit still halts, hold the power button for ten seconds to force a hard reset, then reboot on mains power.