Huawei FreeBuds 3 Replacement Battery HB681636ECW 3.82V 400mAh

Huawei FreeBuds 3 — 3.82V Li-Polymer Replacement Battery (HB681636ECW)

This is a 3.82V, 400mAh Li-Polymer cell that fits individual earbud units in the Huawei FreeBuds 3. It replaces the original HB681636ECW when the existing cell has degraded to the point where active noise cancellation or wireless connectivity can no longer be sustained. Dimensions are 34.40 × 15.45 × 6.70mm — verify clearance before fitting.

• FreeBuds 3 earbud cell: Each earbud carries its own independent cell. The FreeBuds 3 BMS manages charge independently per earbud via the charging case contacts. A degraded cell in one unit causes asymmetric playback — the affected earbud drops out while the other stays active.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the FreeBuds 3 platform. The BMS accepted the new cell without error flags, and the case registered both units as charging simultaneously across all contact positions.
• Case-contact charging tip: After fitting, seat the earbud firmly in the case and leave it for a full charge cycle before use. The FreeBuds 3 case needs to log the new cell state before the companion app reports an accurate charge level — incomplete seating during this first cycle causes the app to show erratic percentages.

Why the FreeBuds 3 cuts out mid-playback on a new cell

The FreeBuds 3 combines active noise cancellation processing with a Bluetooth radio in a very small housing. That combined draw causes voltage to sag briefly at the cell level, and if the new cell hasn't completed its first full charge cycle, the BMS reads that sag as an undervoltage condition and cuts the earbud off. This is not a faulty cell — it resolves after two to three full charge cycles as the cell reaches its rated capacity. Until then, ANC draw alone can be enough to trigger a momentary cutoff on a partially conditioned cell.

Huawei app showing mismatched battery levels between earbuds after replacement

After replacing one earbud cell, the Huawei AI Life app often displays a lower percentage for the replaced unit than the untouched one — even when both have been charged together in the case. This happens because the case calibrates each cell's state-of-charge curve independently, and the new cell starts from a default storage voltage of around 3.7–3.8V rather than a known baseline. Run three full charge-and-use cycles with both earbuds active to let the BMS recalibrate. After that, readings between the two units should align within a few percentage points.