About this replacement
Bose SoundWear Companion — 3.7V Li-Polymer Replacement Battery (AHS803040)
This 3.7V, 1000mAh Li-Polymer cell replaces the original AHS803040 battery inside the Bose SoundWear Companion neck-worn speaker. It fits the wearable's internal battery bay and restores charge capacity lost to cell aging. Voltage and connector match the OEM spec exactly.
- SoundWear Companion fitment: The SoundWear Companion runs a single Li-Polymer cell at 3.7V nominal. The onboard BMS manages charge termination and low-voltage cutoff for that specific cell configuration. This replacement matches the cell dimensions (42 × 30 × 8mm) and voltage rail so the BMS handshake completes without fault codes.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the SoundWear Companion platform. The BMS accepted the cell on first insertion, charge termination triggered correctly at 4.2V, and low-voltage cutoff engaged before the cell dropped below 3.0V under audio load.
- Fuel gauge reset after swap: After fitting a new cell, run the SoundWear Companion down to the low-battery warning before the first full recharge. The onboard fuel gauge recalibrates against actual cell capacity on that first full cycle — skipping this leaves the indicator inaccurate from day one.
Capacity fade from constant top-off charging on the SoundWear Companion
The SoundWear Companion sits on a desk or charges in a bag between uses, which means most cells spend long stretches held at 4.2V. Li-Polymer cells age faster at full charge than at partial charge — sustained high-state storage accelerates electrolyte breakdown. Once capacity drops below 70%, the fuel gauge also drifts because the BMS calibration table no longer matches actual cell behavior. Letting the cell discharge below 20% at least once a month before a full recharge slows this degradation and keeps the fuel gauge accurate.
Audio distorting before the battery indicator reaches empty
An aged or low-capacity cell sags under the combined draw of the amplifier and Bluetooth radio before the indicator shows low battery. The amplifier clips when supply voltage drops below the threshold it needs for clean output, which causes audible distortion at normal listening volumes. The fuel gauge reads the resting voltage, not the loaded voltage, so it can show 20–30% charge while the cell is already sagging under load. Replacing the cell restores the voltage headroom the amplifier needs and eliminates clipping before the indicator reaches empty.