Opus X Wireless Headset Replacement Battery 3.7V 700mAh

Opus X — 3.7V Li-Polymer Replacement Battery

This is a 3.7V, 700mAh lithium-polymer battery for the Opus X wireless headset. It replaces a depleted or degraded original cell and restores the headset to full operation. Fits the Opus X only — confirm your model before ordering.

• Opus X platform fit: The Opus X runs a single Li-Polymer cell at 3.7V nominal. This replacement matches that voltage rail and the physical footprint (50.90 × 33.40 × 3.70mm), so the cell seats correctly inside the headset housing and connects to the onboard charge circuit.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, monitoring BMS cutoff points at both ends. The protection circuit tripped cleanly at low-voltage threshold and accepted charge current without fault flags on a standard DECT base station.
• First-cycle base station logging: Place the headset in the base station and run a complete charge cycle before taking a call. DECT headsets use the base to log the new cell — until that first full cycle completes, the talk-time indicator will not read accurately.

Base station showing a charging error after fitting the new cell

A new Li-Polymer cell ships at storage voltage — typically 3.6–3.85V, not the 4.2V full-charge level. Some DECT base stations flag this as a fault because they expect a recently used pack, not a fresh one at an unfamiliar state of charge. Seat the headset firmly in the cradle and leave it undisturbed for at least one full charge cycle. Once the BMS completes the first handshake with the base, the error clears and normal charging resumes.

Headset cutting out mid-call even with a charged battery

The Opus X draws current from two loads simultaneously — the audio processing circuit and the DECT radio transmitter. Under that combined draw, a cell with any internal resistance will sag in voltage briefly. If the sag drops below the BMS protection threshold, the circuit cuts power to protect the cell. A brand-new replacement cell has minimal internal resistance, so cutouts on a fresh pack usually mean the cell has not completed its first full conditioning cycle. Run three to five complete charge-discharge cycles through the base station and the cutout behaviour should stop. If it continues after five cycles, measure resting voltage — it should sit at 4.1–4.2V after a full charge.