Sennheiser Momentum MTW Earbud Compatible Battery 3.7V 500mAh

Sennheiser Momentum True Wireless MTW — 3.7V Li-Polymer Replacement Battery (AHB702535PCT-01)

This 3.7V, 500mAh Li-Polymer cell replaces the internal battery in Sennheiser Momentum True Wireless MTW and M3IETW earbud units. It fits individual earbud housings where the original cell has degraded through charge cycles. Dimensions are 36 x 25 x 6mm — match these exactly before fitting.

• MTW and M3IETW earbud compatibility: These models share the same compact earbud housing, connector pinout, and BMS handshake logic. The AHB702535PCT-01 part number covers the full MTW lineup, including Momentum 3 Wireless and M3AEBT variants, because Sennheiser used the same cell specification across that generation.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on MTW earbud units. The BMS accepted the new cell without error flags, completed the protection circuit handshake, and held voltage within spec across the full discharge curve.
• Base station logging on first use: Place the freshly fitted earbud in the charging case and run one complete charge cycle before use. The case firmware logs the new cell's capacity baseline during this first cycle — skipping it causes the charge indicator to misread remaining capacity for the first several sessions.

Why MTW earbuds cut out mid-call on a replacement cell

The MTW draws from a single small cell while running Bluetooth audio, the DECT radio, and the onboard DSP simultaneously. That combined load can momentarily pull cell voltage below the BMS cutoff threshold, triggering a protection trip that looks like a dropoff or cutout. A new cell showing 100% charge from the case does not mean it has been fully conditioned — the cell's internal resistance is still settling over the first three to five cycles. Allow three full charge-discharge cycles before judging call stability.

Case shows full charge but earbud shuts off after brief use

This happens when a replacement cell arrives at storage voltage — typically around 3.6–3.7V — and the case interprets that resting charge as full. The cell has not been cycled yet, so usable capacity is well below its rated 500mAh. Seat the earbud in the case, let it complete a full uninterrupted charge to the case's termination point, then discharge it fully once through normal use. After that first full cycle, the case charge indicator will reflect actual cell state accurately.