About this replacement
Marshall Emberton Series — 7.4V Li-ion Replacement Battery (C406A2)
This is a 7.4V, 3350mAh (24.79Wh) Li-ion replacement battery for the Marshall Emberton and Emberton II portable Bluetooth speakers. It fits models 1001908 and 1005696, along with two additional Emberton variants sharing the same battery cavity and connector. When the original cell degrades, audio cuts short and the speaker charges inconsistently — this battery restores normal operation.
- Emberton and Emberton II compatibility: Both generations use the same 7.4V cell architecture, connector pinout, and BMS handshake. The C406A2 and C406A2-2 part numbers are interchangeable across these models — the revision suffix reflects a cell sourcing change, not a wiring difference.
- Bench tested on actual hardware: We ran this battery through charge cycles on an Emberton II unit. The BMS accepted charge from USB-C without fault codes, held voltage under combined amplifier and Bluetooth radio draw, and did not trigger low-voltage cutoff prematurely at high playback volume.
- Monthly discharge cycle for Emberton users: Let the speaker drain below 20% at least once a month before plugging in. The Emberton spends most of its life in a bag or on a desk, constantly topped off. That shallow-cycle pattern causes fuel gauge drift over time — the indicator reads full while actual capacity has quietly dropped.
Audio distorting before the battery indicator reaches empty
As a Li-ion cell ages, internal resistance rises. At high playback volume, the amplifier draws a sharp current spike. A weakened cell cannot sustain voltage through that spike, so the output sags briefly below the amplifier's clean operating threshold — you hear distortion or clipping even though the indicator still shows charge. This is not a speaker fault. The new cell restores low internal resistance, so voltage holds steady through high-draw peaks. After fitting the replacement, confirm the cell is reading above 7.0V under load before closing the housing.
Speaker won't wake from USB-C after sitting discharged for weeks
A deeply discharged Li-ion cell can drop below the minimum acceptance voltage for USB-C Power Delivery handshake — the charger queries the port, gets no valid response, and delivers nothing. The speaker appears completely dead even with a cable connected. Apply a 5V source directly to the battery terminals at a low trickle current (under 100mA) for 10–15 minutes to bring the cell voltage back above 3.0V per cell, which is approximately 6.0V at the pack level. Once the cell recovers to that threshold, plug into USB-C and the PD negotiation will complete normally.