About this replacement
Bose SoundLink / SoundTouch 20 — 11.1V Li-ion Replacement Battery (330107)
This 11.1V 3400mAh Li-ion battery replaces the original pack in the Bose SoundLink, SoundLink 3, and SoundTouch 20 portable wireless speakers. It fits units using OEM part numbers 330107, 330107A, 359495, 359498, 330105, 330105A, 404600, and 404900. Swap it in when your original pack no longer holds a charge or the speaker shuts off unexpectedly during playback.
- SoundLink and SoundTouch 20 compatibility: These models share the same 11.1V three-cell Li-ion architecture, connector pinout, and BMS handshake protocol — which is why one pack covers the full range. The fuel gauge talks directly to the speaker's charge management circuit over the same signal line across all listed variants.
- Bench tested on actual hardware: We cycled this pack on a SoundLink 3 and SoundTouch 20 under combined amplifier and Bluetooth radio load. The BMS held the cutoff threshold correctly at both low-volume and high-volume draw, and the fuel gauge read accurately from 100% down to the low-battery warning.
- Fuel gauge reset after install: After fitting this battery, run the speaker to the automatic low-battery shutoff before charging it back to full. Skipping this step leaves the fuel gauge calibrated to the old cell's capacity curve, so the indicator will read inaccurately from day one.
Why the SoundLink shuts down at high volume even on a full charge
At high volume, the SoundLink's amplifier pulls a sharp current spike that, combined with the Bluetooth radio draw, can drag cell voltage below the BMS protection threshold for a split second. An aged or degraded cell has higher internal resistance, so the voltage sag under that combined load is steeper and faster. The BMS reads the sag as an undervoltage condition and trips — cutting the speaker off even though the fuel gauge showed a full or near-full pack. A fresh 3400mAh cell with lower internal resistance handles the spike without triggering the cutoff.
Audio distorting before the battery indicator reaches empty
This happens when the cell's actual capacity has faded but the fuel gauge hasn't recalibrated — so the indicator still shows 20–30% while the real voltage is already sagging. The amplifier clips when rail voltage drops too low, producing distortion before the speaker ever reaches its shutoff point. It's a gauge drift problem, not an amplifier fault. Fix it by running the new pack all the way down to the automatic shutoff on the first cycle, then charging uninterrupted to full — this resets the gauge to the new cell's actual 3400mAh baseline.