About this replacement
Marshall Stockwell — 11.1V Li-ion Replacement Battery (TF18650-2200-1S3PA)
This is an 11.1V, 2600mAh Li-ion replacement battery for the Marshall Stockwell portable Bluetooth speaker. It slots into the Stockwell's battery bay and restores power to the amplifier, Bluetooth radio, and control board. Capacity is 2600mAh (28.86Wh) — sourced directly from the product data, not interpolated from third-party figures.
- Stockwell platform fit: The Stockwell runs its amplifier, Bluetooth module, and analog circuitry off a single 11.1V three-cell Li-ion pack. All three subsystems share the same voltage rail, so a degraded cell throws off regulation across the whole board — not just audio output.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the Stockwell board. The BMS held cutoff correctly at both ends — no over-voltage trip on charge, no hard shutdown from under-voltage during sustained audio draw at high volume.
- Fuel gauge recalibration on the Stockwell: Let the speaker discharge below 20% at least once a month before plugging in. The Stockwell's fuel gauge drifts when the pack is constantly topped off without a full discharge cycle, causing the indicator to read full while actual capacity has already dropped.
Why the Stockwell cuts audio and drops Bluetooth at high volume
At peak volume, the Stockwell's Class D amplifier and Bluetooth radio draw current simultaneously. On a worn cell, that combined spike pulls the pack voltage below the amplifier's regulation floor — typically around 9.5V on an 11.1V nominal pack. The BMS reads this sag as a fault condition rather than a load condition. The result is an audio dropout or Bluetooth disconnection that looks like a wireless issue but is actually a voltage event. Replacing the pack with a cell that holds its voltage under combined amp-plus-radio load stops the dropout.
Speaker shows full charge indicator but audio distorts before it reaches empty
This is amplifier clipping under voltage sag — not a software bug. When a degraded cell can no longer sustain 11.1V under load, the amplifier's supply rail droops mid-play. The amp clips the audio waveform before the battery indicator has moved, because the indicator reads resting voltage, not load voltage. The gap between resting and load voltage widens as cells age. Fitting a new pack with consistent internal resistance closes that gap and eliminates the distortion. Confirm the fix by playing at 80% volume and checking that the indicator drops in line with audio output — not ahead of it.