About this replacement
Sony WF-1000XM2 — 3.7V Li-Polymer Replacement Battery (SP561150)
This 3.7V, 280mAh Li-Polymer cell replaces the original SP561150 battery inside the Sony WF-1000XM2 wireless earbud unit. It restores power to the active noise cancellation circuit, Bluetooth radio, and audio driver in a single earbud housing. Dimensions are 51.00 × 10.40 × 5.80mm — verify against the original cell before fitting.
- WF-1000XM2 earbud fit: The WF-1000XM2 runs ANC processing, a Bluetooth 4.2 radio, and audio playback simultaneously off one small cell per earbud. The SP561150 footprint and connector position are specific to this unit — no cross-compatibility with XM3 or XM4 cells.
- Bench tested on actual hardware: We cycled this cell under combined ANC-plus-radio load. The BMS held stable voltage across the draw curve and cut off cleanly at the low-voltage threshold without tripping mid-cycle.
- First charge after fitting: Place the earbud in the charging case immediately after installation and run a complete charge cycle before use. The case needs to log the new cell's charge state — skipping this step causes the battery indicator to read incorrectly from the first use.
Why the WF-1000XM2 cuts out mid-call on a new battery
The earbud draws simultaneously from the ANC processor, the Bluetooth radio, and the audio circuit. That combined current spike — especially when ANC adjusts to a sudden ambient noise change — can pull voltage below the BMS cutoff threshold on a cell that hasn't been conditioned. The BMS interprets the sag as a depleted cell and shuts down the output rail. Running two to three full charge-discharge cycles through the charging case raises the cell's delivery capacity and stabilises the voltage under load.
Charging case shows full but earbud dies quickly after replacement
A freshly installed cell ships at storage voltage — typically around 3.6V — not at full charge. If you seat the earbud and check the case indicator before completing a full charge cycle, the case reads the cell as charged based on contact voltage, not actual state of charge. The earbud then cuts off well before expected. Fix this by leaving the earbud in the case for a full uninterrupted charge cycle — the indicator should show full at or above 4.1V before first use.