About this replacement
Sony WH-H910N / WH-H910 — 3.7V Li-Polymer Replacement Battery (SM-03)
This is a 3.7V, 1000mAh Li-Polymer replacement battery for the Sony WH-H910N and WH-H910 wireless noise-cancelling headphones. It matches the original SM-03 cell specification. Fits directly into the headset housing without modification.
- WH-H910N and WH-H910 compatibility: Both headsets run the same 3.7V single-cell architecture with identical connector pinout and BMS handshake protocol. One cell covers both models.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the WH-H910N. The BMS accepted the pack without fault codes, and the headset's battery indicator reported correctly after the first full charge.
- First-cycle charge protocol for WH-H910N: Place the headset on the charging cable or USB-C source immediately after fitting the new cell. The WH-H910N calibrates its battery gauge on the first full charge — skipping this step causes the indicator to misread state of charge for several sessions.
Why the WH-H910N cuts out mid-call on a new or aged battery
The WH-H910N draws from the battery simultaneously for the DECT radio, active noise cancellation, and audio amplifier. Combined peak draw can spike well above the resting average, which stresses a cell that is either new and not yet at full capacity or aged below 80% health. The BMS trips a undervoltage cutoff when cell voltage dips below the protection threshold under that combined load. A fully charged, conditioned cell handles the spike — a partially charged or degraded one does not.
Headset shows full charge but cuts off after short use
This happens when a replacement cell arrives at storage voltage — typically around 3.6–3.7V — and the headset's fuel gauge has not yet completed a calibration cycle. The gauge reads the resting voltage as "full" but the cell has not been charged to its actual 4.2V upper limit. Run one complete charge from flat to full without interruption. After that cycle, the indicator tracks accurately and the headset runs to its rated capacity.