Huawei FreeLace Compatible Battery 3.7V 120mAh AHB380942TPO

Huawei FreeLace — 3.7V Li-Polymer Replacement Battery (AHB380942TPO)

This is a 3.7V, 120mAh Li-Polymer cell that replaces the original AHB380942TPO battery inside the Huawei FreeLace wireless earbuds. It powers both Bluetooth audio and the onboard control module. Capacity matches the product data exactly at 0.44Wh.

• FreeLace earbud platform: The FreeLace uses a single small-format cell tucked into the USB-C charging module on the neckband. The AHB380942TPO format — 43.00 × 9.25 × 3.80mm — is specific to this geometry. A physically larger or smaller cell will not seat correctly against the charge contacts.
• Bench tested on actual hardware: We ran this cell through charge cycles on the FreeLace platform. The BMS accepted the new pack without error flags. Voltage held steady across combined Bluetooth radio and audio driver draw, with no mid-session cutoff.
• First-cycle charging on the FreeLace: Plug the FreeLace directly into a USB-C source for a full uninterrupted charge before first use. The onboard controller logs the new cell's baseline during this cycle. Skipping it causes the battery indicator to misread state-of-charge for several sessions.

Why the FreeLace cuts out mid-track after a battery swap

The FreeLace draws simultaneously from one cell for Bluetooth radio, audio processing, and the inline control module. If the replacement cell hasn't completed a full first charge, its resting voltage may sit around 3.6V — low enough that combined load pulls it below the BMS undervoltage threshold mid-use. The BMS then trips to protect the cell, which looks like a sudden shutdown. One full charge cycle before first use resolves this — the cell stabilises above 3.7V nominal and sustains the combined draw without tripping.

Talk time shorter than rated on the first few sessions

Li-Polymer cells don't deliver full rated capacity straight out of storage. Internal resistance is slightly elevated until the cell completes three to five full charge-discharge cycles. On the FreeLace, this shows up as noticeably shorter listening time in the first few sessions after a battery swap. No fault exists — capacity increases incrementally with each cycle. After the fifth full cycle, check that the cell is reaching 4.2V at end of charge before concluding there is a capacity issue.