Bose QC3 40229 Replacement Battery 3.7V 200mAh

Bose QuietComfort 3 — 3.7V Li-ion Replacement Battery (40229)

This is a 3.7V, 200mAh Li-ion cell for the Bose QuietComfort 3 headphones. It powers both the active noise cancellation circuit and the audio amplifier inside the QC3 earcup. Fit models include QC3 units referenced under OEM numbers 40229 and 40228.

• QC3 compatibility — OEM cross-reference: The 40229 and 40228 listings share the same cell footprint, voltage rail, and connector orientation. The BMS in the QC3 housing does not require a proprietary handshake, so the cell seats and charges from the original Bose cable without modification.
• Bench tested on actual hardware: We ran this cell through charge-discharge cycles on a QC3 unit, monitoring the BMS cutoff at both ends. The cell accepted a full charge without thermal event, and the low-voltage cutoff triggered correctly before cell damage could occur.
• First-charge protocol for the QC3: The QC3 ships replacement cells at storage voltage, around 3.6V. Plug the headset into the Bose charging cable and let it complete one uninterrupted charge cycle before use — this allows the onboard circuit to register the new cell's actual capacity baseline.

Why the QC3 cuts out mid-listen after a battery swap

The QC3 draws current from two separate loads simultaneously — the audio amplifier and the active noise cancellation circuit. Under combined draw, a new cell at storage voltage can sag below the BMS cutoff threshold, triggering a shutdown that looks like a dead battery. This is not a faulty cell. One full charge cycle from the Bose cable resolves it. After that first cycle, the cell stabilises under combined load and cutouts stop.

QC3 showing full charge on the indicator but cutting off after a few tracks

This happens when the cell arrives at storage voltage (roughly 3.6V) and the QC3's charge indicator reads that as "full" before a proper charge cycle has run. The indicator is calibrated to the cell's state of charge, not its actual capacity. The fix is straightforward — connect to the Bose charging cable and let the LED cycle through to a confirmed full charge, which typically brings the cell to 4.2V. After that first complete cycle, the indicator and actual capacity align.