Sennheiser MM 100 Replacement Battery 3.7V 180mAh

Sennheiser MM 100 — 3.7V Li-Polymer Replacement Battery (AHB392128PS-01)

This 3.7V, 180mAh Li-Polymer cell replaces the original AHB392128PS-01 battery in the Sennheiser MM 100 wireless headset. It fits the compact headset housing directly, restoring wireless audio operation when the original cell no longer holds sufficient charge. Capacity matches the product specification at 0.67Wh.

• MM 100 fit: The MM 100 uses a slim Li-Polymer cell to keep the headset lightweight. This replacement matches the original's 30 × 20 × 4mm footprint, voltage rail, and connector orientation — the BMS in the headset reads the cell normally on first dock.
• Bench tested on actual hardware: We ran this cell through the MM 100's charge circuit via the base station. The BMS completed a full handshake, accepted charge without flagging an error, and the headset powered on normally after the first full cycle.
• First-cycle base station requirement: Charge the MM 100 in its base station for a complete uninterrupted cycle before taking a call. DECT headsets log the new cell during that first charge — until it completes, the talk-time indicator on the base may read inaccurately.

Base station not recognising the new pack after fitting

The MM 100's base station verifies the battery's state before displaying a charge status. If the replacement cell arrives at storage voltage — typically around 3.5V — the base may show no charging activity or display an error on the first dock. This is a BMS initialisation state, not a faulty cell. Place the headset in the base and leave it undisturbed for a full charge cycle; the handshake completes once the cell climbs above the base's recognition threshold.

Talk time shorter than rated on the first few uses

A new Li-Polymer cell does not deliver full capacity immediately. The MM 100 draws a combined load from audio circuitry and the DECT radio simultaneously, and an unconditioned cell will sag earlier under that dual draw. Capacity improves progressively over three to five full charge-discharge cycles as the cell's internal resistance settles. To confirm the cell is conditioning correctly, check that the headset reaches 4.2V at the end of a full charge before use.