About this replacement
Marshall Emberton / Emberton II — 7.4V Li-ion Replacement Battery (C406A2)
This 7.4V, 2600mAh Li-ion battery replaces the original C406A2 cell in the Marshall Emberton and Emberton II portable Bluetooth speakers. It fits models 1001908 and 1005696 among others. Capacity is 19.24Wh — matching the original pack specification.
- Emberton and Emberton II compatibility: Both generations share the same battery bay dimensions, connector pinout, and BMS handshake protocol — the C406A2 cell works across all listed model numbers without modification.
- Bench tested on actual hardware: We cycled this pack through the Emberton's charge controller and verified the BMS communicated cleanly — protection thresholds engaged at the correct cutoff voltages with no false trips under combined amplifier and Bluetooth radio draw.
- Monthly discharge cycle for the Emberton: The Emberton is typically left on a desk charging constantly. Let the battery drop below 20% at least once a month before recharging — without a periodic full discharge, the fuel gauge drifts and the speaker will misread remaining charge, cutting out unexpectedly while the indicator still shows bars.
Audio distortion before the battery indicator reaches empty
As a Li-ion cell ages or sits in deep discharge, its internal resistance rises. Under the combined current draw of the Class D amplifier and Bluetooth radio at high volume, the pack voltage sags below the amplifier's stable operating threshold before the fuel gauge registers empty. The amplifier clips — you hear crackling or thinning audio — while the indicator still shows charge. A new cell with lower internal resistance holds voltage above that threshold. If distortion starts early in a listening session even on a new battery, charge the pack fully to 8.4V before use.
Emberton won't wake from USB-C after sitting unused for months
If the Emberton sits uncharged for an extended period, the cell can drop below the USB-C Power Delivery minimum acceptance voltage — typically around 2.5V per cell. At that level, the charger handshake fails and the speaker appears completely dead. Plug in a USB-C cable and leave it connected for at least 20–30 minutes without expecting any indicator light immediately — the BMS requires a trickle precharge phase to bring the cell back above the PD threshold before normal charging begins. If the indicator still shows nothing after 30 minutes, check the cable can deliver at least 5V/1A.