Shure SB901 MXW1 Wireless Transmitter Replacement Battery 3.7V 850mAh

Shure MXW1 / MXW6 / MXW8 Wireless Transmitters — 3.7V Li-ion Replacement Battery (SB901)

This 3.7V, 850mAh (3.15Wh) Li-ion cell replaces the OEM SB901 battery in the Shure MXW1, MXW6, and MXW8 wireless transmitters. These are body-pack and handheld transmitters used in live sound, boardroom, and broadcast applications — not portable speakers. When the original cell degrades, transmit power becomes unstable and audio dropout increases.

• MXW1, MXW6, and MXW8 compatibility: All three transmitters run the same 3.7V battery rail with the same SB901 form factor and connector. The BMS handshake is identical across the series, so a single cell covers all three units without modification.
• Bench tested on actual hardware: We cycled this cell through the MXW charging cradle and confirmed BMS communication, charge acceptance, and full-capacity recognition across multiple charge cycles. The transmitter reported correct charge state throughout.
• Cradle charging tip for MXW transmitters: The MXW charging dock cuts off at 4.2V and will not restart a trickle charge on a cell that drops below roughly 2.5V from long-term storage. If a transmitter shows no charge activity after seating in the cradle, allow 15–20 minutes — the BMS may be in recovery mode before the main charge cycle starts.

Why the MXW transmitter reports full charge but drops audio mid-performance

A degraded SB901 cell can pass the cradle's charge check at rest but sag sharply once the RF transmit circuit draws current. The RF stage in the MXW1 pulls a brief current spike on each transmit burst. If internal cell resistance has risen from age or shallow cycling, terminal voltage drops below the transmitter's minimum operating threshold during that spike. The unit cuts audio to protect the RF circuitry, even though the fuel gauge still shows charge remaining. Replacing the cell resets internal resistance to factory levels and eliminates the sag-induced dropout.

MXW transmitter not recognised by charging cradle after extended storage

If an MXW transmitter sits unused for several months, the SB901 cell can self-discharge below 2.5V — the minimum voltage the cradle's BMS accepts to begin a standard charge cycle. The cradle LED may blink an error code or show no activity at all. Remove the transmitter, wait 60 seconds, and reseat it firmly — some cradle firmware versions retry the handshake on reinsertion. If the cradle still shows no charge activity after two reseating attempts, the cell is below recovery threshold and replacement is the correct fix.