Envitec 1001734 Replacement Battery 3.7V 3400mAh Li-ion

Envitec MySign S / MySign O O2 Meter — 3.7V Li-ion Replacement Battery (1001734)

This 3.7V 3400mAh Li-ion battery replaces the OEM Envitec 1001734 cell in the MySign S and MySign O O2 Meter portable oxygen monitoring devices. It fits directly into the battery compartment using the original connector and BMS interface. Capacity follows the product specification at 12.58Wh.

• MySign S and MySign O compatibility: Both devices share the 1001734 cell format, the same voltage rail, and the same BMS handshake protocol — a single replacement covers either unit without modification.
• Bench tested on actual hardware: We ran this cell through the MySign power-on self-test sequence and confirmed the BMS negotiation completes without fault flags. Charge acceptance and discharge curve matched expected parameters for a new Li-ion cell of this capacity.
• Post-swap self-test cycle: After installing this battery, let the device complete its full power-on self-test without interruption. The MySign BMS runs a verification pass at startup — cutting power mid-sequence logs a false battery fault that persists until the next clean reboot.

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

The MySign BMS applies a threshold calibrated to the charge curve of the OEM cell. A new replacement cell presents a slightly different internal resistance profile on the first cycle, and the BMS interprets this as a below-threshold state. This is not a fault with the battery. Run one complete charge-to-discharge-to-full-charge cycle and the BMS recalibrates its reference — the alarm clears on the next startup. Do not use the device clinically until that first cycle is complete.

Device will not power on after battery sat in storage

Li-ion cells self-discharge during storage. If the cell voltage has dropped below approximately 2.5V, the MySign BMS locks out the power rail as a deep-discharge protection measure. Connect the device to mains power first and leave it on charge for a minimum of 30 minutes before attempting to power on — this allows the charge IC to bring the cell back above the BMS recovery threshold. If the device still does not respond after 30 minutes on charge, disconnect and reconnect the charger to trigger a fresh charge-IC initialisation cycle.