About this replacement
Phonak ComPilot / ComPilot II — 3.7V Li-Polymer Replacement Battery (IP462539)
This 3.7V, 300mAh lithium-polymer cell replaces the original battery in the Phonak ComPilot and ComPilot II audio streamers. Both devices use the same OEM pack (IP462539) and share an identical battery bay and connector. Capacity figures come from product data — 300mAh / 1.11Wh.
- ComPilot and ComPilot II compatibility: Both generations run the same 3.7V Li-Polymer cell with the same physical footprint (36.80 × 24.50 × 4.60mm), BMS pinout, and connector. Phonak carried the pack forward unchanged between revisions, so one SKU covers both.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a ComPilot unit, monitoring BMS communication and cutoff thresholds. The protection circuit trips correctly at low-voltage and the cell accepts a full charge without error flags from the base station.
- First-charge protocol for ComPilot: Seat the ComPilot in the charging cradle immediately after fitting this cell and let the base complete one uninterrupted full charge before use. The base station logs the new cell during this cycle — skipping it causes the battery indicator to display inaccurate charge levels for several sessions.
Why the ComPilot cuts out mid-stream on a new battery
The ComPilot runs two simultaneous loads — audio decoding and Bluetooth radio transmission. When the cell is fresh out of packaging it sits at storage voltage, typically around 3.6–3.7V, which is below the operating headroom the BMS expects under combined draw. That gap causes brief undervoltage trips that look like audio dropout or full shutdown. One complete charge cycle in the cradle brings the cell to 4.2V and stabilises the BMS, stopping the cutouts.
Base station shows solid charge light but ComPilot shuts off after a short session
A solid charge light on the base means the charger IC detected the cell and stopped pushing current — it does not confirm the cell reached full capacity. A cell delivered at storage voltage can satisfy the charger's termination condition before hitting 4.2V, leaving usable capacity on the table. Pull the ComPilot from the cradle, wait 10 seconds, reseat it, and let it charge without interruption until the indicator light changes state naturally. Check open-circuit voltage with a multimeter at the pack contacts — it should read 4.15–4.20V before you rely on it for a full session.